MARS 


BY 

WILLIAM  H.  PICKERING 


HARVARD  ASTRONOMICAL  STATION,   JAMAICA 


BOSTON 

RICHARD  G.  BADGER 

THE  GOBHAM   PRESS 


A\ 


COPTBIQHT,  1921.  by  ftlCHABD  G.  BADO1 

All  Rights  Reserved 


Made  in  the  United  States  of  America 
The  Gorham  Press,  Boston,  U.  8.  A. 


PREFACE 

The  following  list  of  Collected  Papers  on  Mars  con- 
tains all  those  of  importance  prepared  by  the  author 
between  1890  and  1914.  Excepting  the  first  and  the 
last,  they  are  arranged  in  chronological  order.  All 
have  been  revised,  and  some  of  them  shortened.  No 
important  additions  have  been  made,  yet  it  is  believed 
that  it  will  be  found  that  they  represent  very  satisfac- 
torily the  latest  modern  views  on  the  physical  conditions 
of  the  planet's  surface. 

WILLIAM  H.  PICKERING. 

Mandeville,  Jamaica,  B.  W.  I. 
August,  1921. 


454919 


CONTENTS 

CHAPTEB  PAQB 

I.    FACTS  ABOUT  MARS 11 

Peculiarities  of  the  Planet 
The  Shifting  Marshes 

II.    PHOTOGRAPHS  OF  A  SNOW  STORM  ON  MARS   ...  21 

III.  THE  GLACIAL  PERIOD  AND  THE  PLANET  MARS    .     .  24 

IV.  COLORS  EXHIBITED  BY  THE  PLANET  MARS     ...  26 
V.    CHANGES  AND  FLOODS  ON  MARS 42 

VI.    MARS  IN  1892 56 

VII.      SCHIAPARELLI'S  LATEST  VlEWS  REGARDING  MARS      .         64 

The  Planet  Mars  by  Giovanni  Schiaparelli 

VIII.    THE  SEAS  OF  MARS 97 

IX.    RECENT    STUDIES    OF    THE    MARTIAN    AND    LUNAR 

CANALS 103 

X.    AN   EXPLANATION   OF   THE   MARTIAN   AND   LUNAR 

CANALS 108 

XI.    THE  DOUBLE  CANALS  OF  MARS 113 

XII.    THE  MARTIAN  SNOWS 116 

XIII.  WHAT  WE  KNOW  ABOUT  MARS 120 

The  Orbit  of  Mars 

Gravitation,  Water  and  Atmosphere 

Climate  and  Meteorology 

Seas,  Canals  and  Lakes 

Duplication  of  the  Canals 

Seasonal  Changes 

Is  the  Planet  Inhabited  by  Intelligent  Beings? 

XIV.  DIFFERENT  EXPLANATIONS  OF  THE  CANALS  OF  MARS  .     147 
XV.    SIGNALLING  TO  MARS 158 

XVI.    THE  CANALS  OF  MARS 162 

XVII.    MARS— THINGS  KNOWN  AND  SURMISED      ....     167 
INDEX  ...     173 


MARS 


MARS 


CHAPTER  I 
FACTS  ABOUT  MARS  x 

Mars  is  to  many  persons  the  most  interesting 
body  in  the  heavens,  chiefly  because  it  exhibits  phe- 
nomena that  we  cannot  explain  unless  we  assume 
that  life  in  some  form  or  other  exists  there. 

Before  describing  the  more  recent  observations  of 
Mars,  it  is  well  to  mention  a  few  astronomical  facts 
about  the  planet  that  are  more  or  less  familiar. 
Mars  revolves  in  an  orbit  outside  that  of  the  earth 
in  a  period  a  little  short  of  two  years,  and  we  over- 
take it  on  an  average  once  in  every  two  years  and 
fifty  days.  I  say  on  an  average,  because  the  orbit 
of  Mars  is  very  eccentric,  and  the  time  we  need  in 
order  to  catch  up  with  it  varies  appreciably;  it  is 
longer  when  we  overtake  it  in  August  than  when 
we  do  so  in  February.  The  date  on  which  we  over- 
take and  pass  it  is  called  the  date  of  opposition, 
because  the  planet  is  then  just  opposite  the  sun, 
and  rises  at  sunset.  In  August,  when  Mars  is  near- 

1  Youth's  Companion,  1917,  91,  639. 
11 


12      :•'.•••  'Mara 

est  the  sun,  we  approach  to  within  35,000,000  miles 
of  it,  but  at  a  February  opposition  we  do  not  get 
nearer  than  62,000,000  miles.  The  day  of  Mars  is 
about  forty  minutes  longer  than  ours,  and  the  in- 
clination of  its  axis  to  its  orbit  virtually  the  same 
as  ours,  23.5°. 

PECULIARITIES  OF  THE   PLANET 

The  diameter  of  Mars  is  4230  miles — only  a  lit- 
tle more  than  half  that  of  the  earth;  and  the  force 
of  gravity  on  its  surface  is  about  two-fifths  as  great 
as  that  on  the  surface  of  the  earth.  That  fact  is 
of  the  greatest  importance  to  the  life  on  Mars,  for 
because  of  it  the  atmospheric  pressure  on  its  sur- 
face is  probably  not  much  more  than  one-tenth  of 
our  own.  The  boiling  point  of  water  on  Mars, 
therefore,  is  only  about  115° ;  if  Mars  were  as  warm 
as  the  earth,  water  would  boil  when  merely  exposed 
to  the  sun. 

Snow  melts  at  the  same  temperature  on  Mars 
that  it  does  on  the  earth,  namely  32°.  When  the 
north  pole  of  Mars  is  turned  toward  the  sun,  the 
huge  snow  fields  that  surround  it  melt  rapidly,  and 
large  dark  areas,  which  sometimes  cover  two  mil- 
lion square  miles,  form  round  them.  These  are  un- 
doubtedly marshes. 

At  times  certain   parts  of  the  marshes  become 


Facts  About  Mara  13 

dark  blue  in  color,  and  we  believe  therefore  that 
those  parts  are  lakes.  Although  they  are  usually 
confined  to  the  regions  that  surround  the  polar 
snowcaps,  they  sometimes  appear  in  other  parts  of 
the  planet.  None  of  them  are  permanent,  however; 
the  blue  color  seldom  lasts  more  than  a  few  weeks. 
We  suppose,  therefore,  that  they  are  shallow,  and 
that  the  water  evaporates  rapidly  under  the  low 
atmospheric  pressure. 

Often  great  indistinct  yellowish-white  bodies  rise 
from  the  marshes  and,  as  the  planet  revolves  on  its 
axis,  follow  them  across  the  face  of  the  disk.  We 
can  hardly  doubt  that  these  objects  are  clouds  and 
fog. 

When  the  polar  caps  are  melting,  the  atmosphere 
of  Mars  contains  as  much  water  vapor  as  our  own, 
but  much  less  of  the  permanent  gases.  Because  of 
that,  and  of  the  low  temperature  of  the  boiling 
point,  evaporation  and  condensation  occur  much 
more  rapidly  on  Mars  than  on  the  earth.  As  a  re- 
sult their  atmosphere  at  sunrise  and  sunset  is  full 
of  cloud,  which  probably  lasts  all  night.  These 
cloudy  nights  help  to  keep  the  planet  warm,  and  the 
clear  days  also  tend  to  warm  it  up.  Except  near 
the  equator,  however,  the  climate  on  Mars  must  be 
subject  to  great  extremes  of  temperature,  and  its 
nights  are  without  much  doubt  bitterly  cold.  Of 
one  thing  we  can  be  quite  sure:  to  beings  consti- 


14,  Man 

tuted  like  ourselves  the  climate  there  would  be  very 
disagreeable. 

The  surface  of  Mars  may  be  roughly  divided  into 
two  parts — the  dark  areas  and  the  bright  ones. 
The  dark  areas  were  formerly  supposed  to  be  seas 
and  the  bright  areas  continents,  but  now  we  know 
that  that  is  not  the  case,  and  that  there  are  no 
permanent  seas  on  Mars.  What  seems  more  likely 
is  that  the  regions  that  are  permanently  dark  are 
areas  covered  with  vegetation;  that  those  that  are 
temporarily  dark  are  marshes;  and  that  the  bright 
regions  are  deserts.  Crossing  both  the  dark  and  the 
bright  regions  we  find  a  network  of  canals — per- 
haps not  so  many  as  are  shown  by  some  observers, 
but  certainly  a  large  number.  At  the  junction  of 
the  canals  with  one  another,  and  with  the  seas,  we 
often  find  little  dark  spots,  which  we  call  lakes. 

Of  course  we  do  not  call  them  canals  and  lakes 
in  the  terrestrial  sense  of  the  words.  Those  are 
merely  names,  just  as  we  call  dark  markings  on  the 
planet  seas.  We  do  not  know  yet  what  the  canals 
and  lakes  really  are,  but  of  one  thing  we  are  fairly 
certain,  and  that  is  that  they  are  not  water.  Prob- 
ably, like  the  seas,  they  are  strips  covered  with 
vegetation.  Of  course  there  may  be  some  water  in 
them.  The  polar  seas  are  really  marshes,  and  the 
same  may  be  true  of  the  ephemeral  canals — those 
that  are  short-lived  and  that  soon  dry  up. 


Facts  About  Mars  15 

Some  observers  believe  that  each  canal  contains 
a  central  ditch  or  pipe  by  which  the  canal  is  irri- 
gated, and  that  what  we  see  is  the  vegetation  grow- 
ing in  that  irrigated  region.  They  believe  that  the 
main  object  of  the  canals  is  to  conduct  water  from 
the  polar  caps  to  the  great  so-called  seas,  situ- 
ated in  the  southern  hemisphere  of  the  planet,  and 
that  huge  engines  pump  the  water  through  those 
pipes  or  ditches.  One  writer  has  even  gone  so  far 
as  to  compute  what  horse  power  would  be  necessary 
to  accomplish  that  task,  and  finds  that  it  would 
require  about  four  thousand  times  the  amount  of 
power  that  Niagara  gives. 

THE  SHIFTING  MARSHES 

All  these  conjectures  seem  to  other  observers 
most  improbable.  If  the  snow  at  one  pole  of  the 
planet  is  exposed  to  continuous  sunlight,  under 
which  it  melts  rapidly,  it  adds  a  great  deal  of  water 
vapor  to  the  atmosphere,  and  so  increases  the  pres- 
sure; if  the  other  pole  is  exposed  continuously  to 
the  terrible  cold  of  interplanetary  space,  it  has 
scarcely  any  atmosphere  to  protect  it.  We  cannot 
doubt  therefore  that  strong  atmospheric  currents 
must  pass  from  the  sunlit  pole  to  the  other,  bearing 
the  water  vapor  with  them.  In  fact,  we  know  that 
that  is  the  case,  for  we  can  see  that  the  snow  is 


16  Mart 

transferred  from  pole  to  pole  and  back  again  every 
year  by  a  process  of  distillation  and  condensation. 

Indeed  it  seems  to  me  that  the  hard  thing  to  un- 
derstand is,  not  how  the  water  may  be  transported 
across  the  planet,  but  rather  how  it  may  be  kept 
from  going  too  fast  and  leaving  the  intermediate 
surface  a  waterless  desert  for  a  large  part  of  every 
half  year.  If  the  so-called  canals  have  some  func- 
tion to  perform  in  the  tremendous  transportation 
scheme  on  Mars,  it  is  surely  not  that  of  conduits  but 
rather  that  of  reservoirs  to  hold  back  the  flow. 
For,  with  the  low  atmospheric  pressure  on  the  planet, 
the  evaporation  from  every  liquid  or  moist  surface 
must  be  intense. 

If  a  current  of  air  bearing  moisture  sets  south 
from  a  certain  point,  let  us  say  a  large  marsh  near 
the  north  pole,  it  will  not  long  retain  that  direction. 
When  it  starts  it  is  moving  not  only  south  over  the 
surface  but  also  toward  the  east  with  the  surface 
of  the  planet,  as  it  revolves  on  its  axis.  As  the  cur- 
rent of  air  gets  farther  and  farther  away  from 
the  pole,  the  underlying  surface  travels  faster  and 
faster;  thus  the  air  current  that  it  leaves  behind 
seems  to  blow  toward  the  west  as  well  as  toward  the 
south;  that  is,  it  seems  to  come  from  the  northeast. 
We  are  quite  familiar  with  this  phenomenon  on  the 
earth,  under  the  name  of  the  trade  winds. 

When  the  sun  rises  on  such  a  polar  marsh  or 


Fact  $  About  Mart  17 

lake,  the  water  at  once  begins  to  evaporate.  It 
does  not  generally  form  a  cloud,  however,  but  re- 
mains a  transparent  volume  of  vapor  or  gas,  mov- 
ing slowly  southward.  When  night  falls  it  con- 
denses to  a  cloud,  and  much  of  it  remains  in  that 
condition  until  the  following  morning,  when  we  see 
it  following  the  marsh,  and  sometimes  at  one  or 
two  hundred  miles  distant  from  it.  The  part  of  the 
cloud  that  does  not  remain  in  that  condition  through 
the  night  must  be  precipitated  on  the  surface  as 
snow.  When  the  sun  again  rises  on  it,  it  will  melt, 
and  thus  moisten  the  western  or  following  side  of 
the  marsh,  while  the  eastern  side  gradually  dries 
up.  If  the  surface  of  Mars  is  very  level,  as  we 
believe  to  be  the  case,  and  if  our  reasoning  is  cor- 
rect, those  marshes  should  then  be  found  to  shift 
their  positions  slowly,  and  to  travel  southward  and 
westward. 

Now,  that  is  exactly  what  has  been  seen  to  take 
place.  In  December,  1913,  an  observer  drew  a  map 
to  show  the  marshy  region  that  formed  a  part  of 
the  great  marsh  surrounding  the  polar  snowcap  of 
Mars.  In  the  following  January  he  again  ob- 
served that  region,  and  made  another  map.  Much 
to  his  surprise,  he  found  that  the  two  maps  did  not 
agree — that  the  marshes  had  shifted  slightly  toward 
the  west.  At  first  he  thought  he  had  made  a  mis- 
take, but  after  a  little  thought  he  found  the  ex- 


18  Mars 

planation.  Since  then  other  polar  marshes  have 
been  observed,  and  the  same  shift  has  been  seen. 

The  fact  that  the  polar  canals  also  shift  at  times 
with  the  retreat  of  the  snowcap  is  one  of  the  rea- 
sons why  we  believe  that  some  of  the  canals  are 
merely  marshes.  Certain  other  canals  sometimes 
shift,  however,  and  for  no  apparent  reason,  and  in 
no  predictable  direction.  The  same  is  true  of  the 
southern  permanent  seas.  The  canals  are  so  nar- 
row that  we  cannot  tell  what  their  color  is,  but  the 
seas  turn  from  gray  to  green  when  the  moisture 
from  the  polar  caps  first  reaches  them;  the  color 
is  at  times  very  vivid,  so  that  we  feel  fairly  confident 
that  the  seas  at  least  are  areas  of  vegetation. 

If  on  the  earth  an  area  of  the  size  of  our  New 
England  States  should  within  thirty  years  change 
from  a  fertile  plain  to  a  barren  desert,  we  should 
consider  it  as  a  real  catastrophe.  It  is  because  ap- 
parent changes  of  that  character  do  occasionally 
occur  upon  Mars,  and  because  similar  temporary 
changes  occur  frequently,  that  astronomers  find  the 
planet  of  so  much  interest. 

The  temporary  changes  are  most  frequent  at  the 
time  of  the  development  of  the  dark  regions,  which 
occurs  when  the  polar  caps  are  melting  most  rap- 
idly ;  but  astronomers  have  only  begun  to  study 
them  within  the  past  few  years.  Since  no  single  ob- 
server can  keep  all  parts  of  the  planet  under  con- 


Facts  About  Mars  19 

stant  inspection,  an  association  of  observers  inter- 
ested in  Mars  has  been  formed.  These  observers 
are  stationed  in  the  United  States,  in  Japan,  in 
Australia,  in  Asia,  in  Italy,  Denmark,  France,  and 
Great  Britain.  They  send  in  regular  reports  to 
a  central  bureau,  which  publishes  the  results  in  one 
of  the  astronomical  magazines,  whence  they  are  dis- 
tributed to  astronomers  throughout  the  world. 

It  is  easy  to  measure  the  length  of  the  canals,  and 
also  the  breadth  of  the  wider  ones,  but  to  measure 
the  breadth  of  the  narrower  ones  is  more  difficult. 
There  are  many  canals  from  one  thousand  to  two 
thousand  and  even  three  thousand  miles  long.  When 
they  first  appear  they  are  often  more  than  two  hun- 
dred miles,  broad,  but  as  the  season  progresses  they 
narrow,  and  new  and  much  smaller  canals  appear. 
We  have  measured  some  of  these  smaller  canals,  and 
believe  that  some  of  them  are  less  than  ten  miles 
wide.  The  larger  lakes  situated  at  the  junctions  of 
the  canals  are  sometimes  several  hundred  miles  in 
diameter,  but  the  smallest  ones  that  we  can  observe 
are  probably  no  more  than  fifty. 

As  compared  with  our  earth,  it  is  certain  that 
Mars  has  a  scanty  supply  of  several  substances 
needed  to  support  life.  One  of  them  is  water;  the 
Martian  supply  of  that  is  certainly  less  than  one 
one-thousandth  of  what  we  have  upon  the  earth. 
Of  course  it  is  true  that  we  have  a  great  deal  more 


*0  Mart 

water  than  we  need.  Another  necessary  is  nitro- 
gen, which  is  needed  for  plant  food.  We  have  at 
least  forty  times  as  much  of  it  for  each  square  mile 
of  land  surface  as  is  found  upon  Mars.  Another  very 
important  plant  food  is  the  gas,  carbon  dioxide, 
that  our  terrestrial  volcanoes  supply  to  our  vege- 
tation. If  that  supply  should  be  cut  off,  our  vege- 
tation would  soon  die,  and  that  would  be  the  end 
of  all  animal  life  upon  our  planet.  Mars  is  a  world 
more  ancient  than  our  own,  and  it  is  quite  possible 
that  there  is  little  volcanic  activity  there  at  pres- 
ent. If  so,  carbon  dioxide  must  be  in  great  demand. 


CHAPTER  H 

PHOTOGRAPHS  OF  A  SNOW  STORM  ON 
MARS1 

A  box  of  negatives  has  recently  been  received  from 
the  temporary  Harvard  observing  station  upon  Mt. 
Wilson,  California,  and  contains  among  other  things 
a  number  of  plates  of  the  planet  Mars.  Seven 
views  were  taken  April  9,  between  22h.  56m.  and 
£3h.  41m.,  Greenwich  mean  time.  Seven  more  were 
taken  April  10,  between  23h.  20m.  and  £3h.  32m. 
Thus  the  same  face  of  the  planet  was  presented  in 
both  cases.  Distinct  and  identifiable  spots  and  mark- 
ings are  well  shown  in  all  the  pictures,  but  in  those 
taken  on  the  latter  date  a  considerable  accession  is 
shown  to  the  white  spot  surrounding  the  south  pole. 
It  has  been  known  for  years  that  the  size  of  these 
polar  spots  varied  gradually  from  time  to  time,  ap- 
parently diminishing  in  the  summer,  and  increasing 
in  the  winter  of  their  respective  hemispheres.  But 
I  believe  that  this  is  the  first  time  that  the  precise 
date,  and  approximate  extent  of  one  of  these  ac- 


1  Sidereal  Messenger,  1890,  9,  254. 
21 


22  Mars 

cessions  has  been  observed.  The  area  affected 
stretches  from  the  terminator,  which  at  this  time 
was  in  long.  70°,  along  parallel  —  30°  to  longitude 
110°,  thence  to  longitude  145°,  latitude  — 45°; 
thence  to  the  limb  which  was  in  latitude  — 85°  and 
the  220°  meridian,  and  thence  back  to  the  point  of 
starting.  It  may  thus  extend  also  over  an  unknown 
area  on  what  was  at  that  time  the  invisible  hemi- 
sphere of  the  planet.  The  visible  area  included  is 
surprisingly  large,  amounting  to  about  2,500,000 
square  miles  or  somewhat  less  than  the  area  of  the 
United  States.  Being  near  the  limb,  however,  it  is 
not  as  conspicuous  as  might  at  first  sight  be  sup- 
posed. On  the  morning  of  April  9,  the  area  was 
faintly  marked  out  as  if  pervaded  by  haze,  or  by 
small  separated  bodies,  too  small  and  too  far  apart, 
or  too  faint  to  be  recognized  individually.  But  on 
April  10  the  whole  region  was  brilliant,  fully  equal- 
ing that  surrounding  the  north  pole.  In  the  mean- 
time a  much  smaller  area  on  the  limb  which  on  the 
9th  was  very  bright  had  either  vanished  or  joined 
the  main  mass,  by  moving  eastwardly,  as  we  should 
say,  considering  Mars  as  a  globe. 

The  date  of  these  events  corresponds  to  the  end 
of  the  winter  season  on  the  southern  hemisphere  of 
Mars,  or  what  would  be  with  us  about  the  middle  of 
February.  The  numerical  data  given  above  are 


Photographs  of  a  Snow  Storm  on  Mars     23 

founded  on  the  extremely  useful  tables  published  by 
Mr.  Marth  in  the  Monthly  Notices. 

As  to  what  these  observations  mean,  might  most 
naturally  be  explained  by  terrestrial  analogies,  but 
be  that  as  it  may,  the  facts  are  that  these  appear- 
ances are  conspicuous  upon  each  of  the  fourteen 
photographs,  and  so  distinctly  so,  that  no  one  who 
had  once  seen  them  would  hesitate  an  instant  in  de- 
ciding on  which  day  any  particular  plate  was  taken. 


CHAPTER  IH 

THE  GLACIAL  PERIOD  AND  THE  PLANET 
MARS1 

It  seems  to  me  that  one  of  the  chief  secondary 
causes  of  the  Glacial  Period,  as  based  on  an  increased 
eccentricity  of  the  Earth's  orbit,  has  not  heretofore 
been  sufficiently  enforced.  During  the  short  winters 
and  long  summers,  whatever  precipitation  occurs  will 
be  largely  in  the  form  of  rain.  On  the  other  hand, 
during  the  long  winters  and  short  summers  it  will 
be,  on  the  whole,  mainly  in  the  form  of  snow.  Now 
the  snow  by  its  great  reflective  power  will  cause 
the  earth  to  lose  a  very  large  proportion,  perhaps 
nearly  three-quarters,  of  whatever  radiant  energy 
does  fall  upon  it.  Moreover,  during  the  short  sum- 
mer, when  the  sun  is  able  to  melt  the  snow,  there  will 
be  an  extensive  evaporation  from  its  whole  surface, 
forming  clouds.  These  will  in  their  turn  reflect  away 
the  sun's  rays,  and  at  the  same  time  by  their  shade 
protect  the  snow  beneath  them  from  melting. 

This  cause  requires  for  its  action  the  presence  of 

1  Knowledge,  1882,  118. 

24 


The  Glacial  Period  and  the  Planet  Mars     25 

considerable  moisture  upon  the  surface  of  the  planet. 
It  has  been  stated  that  the  glacial  theory  does  not 
appear  to  apply  to  Mars.  In  the  case  of  this  planet, 
however,  we  have  good  reason  for  thinking  that  it 
formerly  had  extensive  oceans  upon  its  surface,  and 
the  gradual  cooling  to  which  it  has  been  subjected 
has  enabled  room  to  be  formed  for  them  in  its  in- 
terior; that  is  to  say,  there  are  probably  extensive 
regions  in  its  interior  which  are  not  sufficiently  hot 
to  convert  water  into  steam.  The  water  would  there- 
fore, naturally,  as  is  the  case  with  the  earth,  go  un- 
derground, filling  all  the  microscopic  cavities  be- 
tween the  rocks.  Be  that  as  it  may,  the  appearance 
of  the  surface  of  this  planet  leads  us  to  think  that 
it  possesses  at  present  very  much  less  water  in  pro- 
portion than  does  our  earth.  That  being  the  case, 
there  could  not  be  sufficient  evaporation  to  form  the 
extensive  snow-caps  required  by  the  glacial  theory. 
As  an  illustration  of  this  point,  we  should  expect  that 
the  northern  or  continental  slopes  of  the  Himalaya 
Mountains  would  be  colder  but  also  drier  than  the 
southern  ones,  which  are  exposed  to  the  ocean.  Yet 
upon  the  warm  southern  slopes  we  find  the  line  of 
perpetual  snow  considerably  lower  than  upon  the 
colder  northern  ones.  Thus,  because  the  supposed 
snow-caps  upon  Mars  are  small,  it  does  not  neces- 
sarily indicate  that  the  temperature  of  the  planet 
is  higher  than  that  of  the  earth. 


CHAPTER  IV 

COLORS  EXHIBITED  BY  THE  PLANET 
MARS1 

The  following  preliminary  account  of  an  investi- 
gation made  in  Cambridge  at  the  last  opposition  of 
Mars,  is  published  at  this  time,  in  the  hope  that 
others  may  take  advantage  of  the  present  favorable 
circumstances,  to  verify  the  results  here  described. 
One  of  the  most  difficult  branches  in  practical  as- 
tronomy is  that  pertaining  to  the  colors  of  the  heav- 
enly bodies,  for  no  other  optical  illusions  can  be 
found  to  be  so  complete  as  those  pertaining  to  color. 
The  planet  Mars  is  frequently  spoken  of  as  the  red 
planet,  yet  its  color  is  by  no  means  as  red  as  that  of 
an  ordinary  candle  flame.  To  illustrate  this  fact,  let 
the  observer  so  place  himself  that  the  planet  Mars, 
an  electric  light,  and  a  candle  or  gas  flame,  all  ap- 
pear to  him  to  be  of  the  same  brilliancy.  He  will 
then  find  that  while  the  planet  is  redder  than  the 
electric  light,  it  is  bluer  than  the  candle  flame,  and 
is,  in  fact,  very  nearly  half  way  between  the  two  in 

1  Astronomy  and  Astro-Physics,  1892,  11,  449. 
26 


Colors  Exhibited  by  the  Planet  Mars        27 

color.     If  either  source  of  light  is  made  brighter 
than  the  other,  its  tendency  is  to  appear  whiter. 

During  the  last  opposition,  sixty  paintings  were 
made  of  the  planet,  with  the  12-inch  Harvard  re- 
fractor, and  sixty-six  uncolored  drawings.  They 
were  all  constructed  upon  a  uniform  scale  of 
200  ooo  ooo  >  ^ne  planet  being  represented  by  a  disc, 
34  millimeters  in  diameter.  Usually  powers  of 
200  to  400  were  employed.  It  was  found  that  in  the 
evening,  the  most  prominent  and  striking  color  of 
the  planet  could  be  represented  very  well  by  car- 
mine. It  was  also  found  that  it  could  be  equally  well 
represented  by  golden  yellow.  When  painted  in  the 
day-time  it  was  orange,  with  more  or  less  carmine, 
depending  on  various  circumstances.  If  a  high 
power  was  used  it  was  much  redder  than  with  a  low 
power.  All  of  these  changes  may  be  readily  ex- 
plained by  the  elementary  principles  of  physics,  but. 
they  illustrate  very  well  some  of  the  difficulties  that 
were  presented  by  the  research.  As  the  planet  is 
illuminated  by  sunlight,  it  is  evident  that  in  order 
to  obtain  a  correct  result,  the  pigment  used  to  repre- 
sent it  should  be  illuminated  by  the  same  source. 
The  paintings  should,  therefore,  be  made  in  the  day- 
time. 

Experiments  were  also  made  in  a  darkened  room, 
the  only  light  transmitted  being  through  a  small 
round  hole  bored  in  the  shutter.  Various  pieces  of 


38  Mars 

colored  stone  were  placed  upon  a  mirror,  which 
reflected  the  light  of  the  sky  into  the  room.  Reflec- 
tions of  these  stones  were  then  viewed  in  two  pieces 
of  flat  glass,  supported  inside  the  room.  By  varying 
the  angles  of  the  glasses,  the  intensity  of  the  sun- 
light reflected  from  the  stones  could  be  varied,  so 
as  to  render  them  either  brighter  or  fainter  than  the 
planet,  as  seen  in  the  telescope.  Paintings  of  the 
planet,  illuminated  by  the  same  light  as  that  used 
in  the  evening,  were  then  compared  with  the  light 
from  the  stones. 

The  other  shutters  of  the  room  were  then  opened, 
and  the  paintings  illuminated  by  daylight.  It  was 
found  that  the  same  laws  of  color  held  good  with 
the  stones  that  had  been  previously  found  appli- 
cable to  the  planet.  The  various  stones  tried  were 
a  piece  of  brown  lava  from  Vesuvius,  a  piece  of  red 
basalt,  a  piece  of  brown  sandstone,  a  piece  of  very 
red  granite,  and  two  pieces  of  brick,  one  an  orange 
red,  and  the  other  the  color  of  dragon's  blood.  The 
former  may  be  best  represented  by  dragon's  blood 
with  a  little  Saturn  red  in  it.  The  red  granite,  which 
is  half  way  in  color  between  the  two  pieces  of  brick, 
is  well  represented  by  dragon's  blood  and  sienna, 
half  and  half.  It  was  found  that  this  piece  of  gran- 
ite under  suitable  illumination  could  be  made  to 
match  exactly  any  of  the  paintings  of  the  planet. 
As  its  color  was  not  far  from  that  of  an  average 


Colort  Exhibited  by  the  Planet  Mart        £9 

brick,  our  next  experiment  was  to  select  a  distant 
building  made  of  brick  of  the  proper  color,  and  make 
a  painting  of  it  as  seen  in  the  telescope.  This  paint- 
ing was  necessarily  made  by  daylight,  and  another 
telescope  had  to  be  used,  as  the  building  was  not 
visible  from  the  dome  of  the  12-inch.  The  building 
selected  was  two  and  a  half  miles  distant.  The  tele- 
scope employed  was  a  6-inch  refractor  by  Clacey. 
The  result  was  as  anticipated,  that  when  the  paint- 
ing of  the  building  was  compared  with  some  of  the 
daylight  paintings  of  Mars,  the  colors  were  identical. 
In  each  case  the  colors  were  separately  mixed  at 
the  time,  although  the  components  were  the  same, 
and  in  each  case  the  result  exactly  satisfied  the  eye. 
The  reason  that  a  red  planet  or  distant  brick 
building  can  be  matched  by  daylight  with  an  orange 
pigment  is  because  of  the  bluish  white  light  reflected 
from  the  atmosphere,  lying  between  the  distant  ob- 
ject and  the  eye,  which  is  mixed  with  the  red  light 
coming  from  the  object,  changing  it  from  red  to 
orange.  If  the  brick  is  examined  close  at  hand,  a 
red  pigment  must  be  employed  to  represent  it.  When 
the  planet  is  viewed  at  night,  or  when  a  piece  of  brick 
near  at  hand  is  illuminated  by  sunlight,  but  the 
pigment  is  illuminated  by  a  yellow  artificial  light, 
this  light  by  enforcing  the  red  components  of  the 
pigment,  and  absorbing  the  blue,  makes  the  pigment 
really  appear  red,  and  therefore  match  the  Sun- 


30  Mars 

illumined  object.  The  object,  therefore,  although 
painted  yellow  by  night,  really  appears  to  the  eye 
redder  than  when  painted  orange  by  daylight.  This 
fact  was  well  brought  out  by  an  experiment  made 
at  night,  employing  the  magnesium  light  instead  of 
the  oil  lamp  as  a  source  of  illumination  for  the  pig- 
ment. In  that  case  the  color  best  matching  the 
planet  was  found  to  be  dragon's  blood  which,  as  we 
have  seen  before,  is  probably  not  far  from  its  true 
color,  which  we  considered  to  be  the  same  as  the 
red  granite,  and  therefore  to  be  represented  by  equal 
parts  of  dragon's  blood  and  sienna. 

But  red  is  by  no  means  the  only  color  visible  upon 
the  planet.  When  near  the  limb,  the  reds  always 
appear  yellowish,  indicating  probably  an  atmo- 
spheric absorption  of  the  red  portion  of  the  spec- 
trum, an  effect  quite  at  variance  with  the  action  of 
our  own  atmosphere,  which  tends  to  absorb  the  blue 
rays. 

Next  to  the  reds  and  yellows,  the  most  important 
colors  are  the  grays  and  greens.  The  latter  colors 
one  would  actually  at  first  attribute  to  an  optical 
illusion,  due  to  contrast  with  the  prevailing  tint. 
If  this  were  the  case,  however,  these  portions  of  the 
planet  should  be  painted  blue,  blue  being  the  com- 
plementary color  of  the  orange  seen  by  daylight. 
Blue  pigment  seen  by  lamp  light  becomes  green, 
which  is  the  complementary  of  the  red  seen  at  night. 


Colors  Exhibited  by  the  Planet  Mars        31 

Therefore  in  either  case  blue  would  be  the  comple- 
mentary color  and  not  green.  Experiments  under 
both  of  these  conditions,  however,  made  upon  sev- 
eral occasions,  conclusively  showed  that  these  greens 
could  not  be  matched  by  blue  pigment  of  any  tint, 
but  were  a  true  and  genuine  green.  Although  rare, 
yet  upon  four  occasions  it  was  noted  that  green 
was  the  most  conspicuous  color  visible.  This  was 
due  sometimes  to  its  covering  a  large  area,  and  some- 
times to  its  being  a  more  intense  color  than  the  red. 
This  also  indicated  that  the  green  could  not  be  due 
to  contrast.  It  was  found  by  experiment  that  the 
effect  upon  green  pigment  produced  by  using  .an 
artificial  illumination  was  very  much  less  marked 
than  upon  red,  the  only  effect  being,  that  when  so 
illuminated,  it  appeared  rather  more  yellow  than 
when  seen  by  daylight.  This  would  imply  that  the 
greens  upon  Mars  were  in  reality  slightly  more  yel- 
lowish than  the  evening  paintings  would  indicate. 

When  the  seeing  became  bad  the  greens  and  reds 
united  to  give  a  whitish  tint,  and  the  colors  dis- 
appeared. This  further  indicated  that  the  greens 
were  not  due  to  contrast.  A  piece  of  black  paper 
was  introduced  into  the  field  of  view  of  the  telescope, 
cutting  off  the  red,  but  the  green  color  remained 
unchanged.  An  examination  was  made  of  Jupiter, 
the  disc  being  a  bright  yellow,  but  no  green  could 
be  detected  upon  it.  The  greens,  especially  the  light 


83  Mart 

greens,  usually  appeared  near  the  poles,  which  were 
necessarily  near  the  edge  of  the  disc,  but  on  these 
occasions  a  region  near  the  center  was  seen  of  a  light 
green  color.  The  green  could  not  therefore  be  at- 
tributed to  the  secondary  spectrum  of  the  glass. 
Moreover,  the  telescope  was  thrown  alternately 
slightly  in  and  out  of  focus,  changing  the  color  of 
the  outside  fringe  of  light,  but  without  altering  the 
green  hue  upon  the  disc. 

The  green  was  not  due  to  atmospheric  refraction 
since  it  was  seen  near  both  poles,  besides  which  the 
color  due  to  this  cause  is  easily  overbalanced  by  that 
due  to  the  lack  of  achromatism  in  the  eyepiece  when 
the  planet  is  placed  near  the  edge  of  the  field.  The 
green  is  not  due  to  an  optical  illusion  caused  by  the 
brightness  of  the  snow.  It  is  sometimes  seen  between 
the  snow  and  the  red  regions  of  the  planet,  and  is 
also  seen  when  the  snow  is  not  visible.  Indeed  I  think 
it  has  been  often  mistaken  for  the  snow,  as  it  is  a 
much  larger  and  more  conspicuous  object.  The  real 
snow  is  much  more  difficult  to  see  than  is  generally 
supposed,  and  is  frequently  not  visible  at  all.  I  have 
only  seen  it  occasionally  when  it  was  readily  dis- 
tinguished by  its  extreme  brightness  and  whiteness. 
An  excellent  idea  of  its  appearance  is  given  in 
Chambers'  Astronomy,  fourth  edition,  and  I  have 
seldom  seen  it  of  much  greater  extent.  The  draw- 
ing is  by  Green,  and  like  all  of  his  work  upon  Mars, 


Colors  Exhibited  by  the  Planet  Mars        33 

is  most  accurate  and  life-like.  The  gray  objects 
upon  Mars,  when  the  seeing  was  poor,  acquired  a 
slightly  yellowish,  and  in  the  day-time  a  brownish 
tint,  owing  to  their  confusion  with  the  surrounding 
regions,  but  when  the  seeing  was  good,  they  were 
either  a  pure  gray,  or  of  a  slightly  greenish  color. 
This  does  not  apply  to  all  the  darker  regions,  as 
we  shall  see  later.  There  was  no  difficulty  in  obtain- 
ing distant  green  terrestrial  objects  to  study  through 
the  telescope,  and  it  was  found  that  even  upon  very 
clear  days,  when  over  two  or  three  miles  distant, 
they  appeared  either  gray  or  greenish  gray.  This 
was  particularly  true  of  the  darker  shades.  In  fact 
I  never  at  any  time  saw  any  colors  as  brilliant  as 
the  bright  greens  upon  Mars.  Even  when  a  piece  of 
bright  red  paper  was  introduced  into  the  field  of 
the  telescope,  no  appreciable  contrast  effect  was 
produced  upon  the  terrestrial  greens.  This  fact, 
together  with  the  other  that  the  greens  on  Mars 
were  seldom  seen  by  daylight,  made  me  think  that 
those  seen  upon  the  planet  must  be  due  to  some 
illusion,  whose  origin  had  not  as  yet  been  eliminated, 
for  one  cannot  well  conceive  of  more  vivid  greens 
than  those  due  to  some  of  our  own  vegetation.  I  had 
been  observing  a  tree  some  two  and  a  half  miles 
distant  with  the  telescope  one  very  clear  morning, 
when  I  noticed  that  there  was  an  electric  lamp  just 
by  the  side  of  it.  That  evening  I  pointed  the  tele- 


34  Mars 

scope  again  on  the  tree,  and  it  instantly  shone  out 
a  most  brilliant  bluish  green,  fully  equalling  in  in- 
tensity anything  I  had  seen  upon  the  planet,  and  a 
trifle  bluer.  This  explained  why  it  was  that  in  the 
da}r-time  I  had  only  detected  the  greens  upon  Mars 
with  difficulty  while  at  night  they  were  conspicuously 
visible, — the  white  light  reflected  by  our  own  atmo- 
sphere had  corrected  them  into  grays. 

Numerous  observations  were  made  of  the  colors 
of  particular  regions,  especially  of  those  which  ap- 
peared very  dark  in  tint.  Attempts  were  also  made 
to  determine  the  color  of  the  canals.  This  latter 
is  an  extremely  difficult  undertaking,  as  the  smaller 
the  area,  the  harder  it  is  to  assign  any  particular 
color  to  it.  The  apparent  area  of  any  very  small 
region  always  strongly  affects  one's  judgment  of  its 
color,  and  in  comparing  two  colors,  it  is  most  im- 
portant that  their  apparent  areas  should  be  equal. 
Regarding  the  colors  of  these  smaller  regions,  as  it 
is  very  desirable  that  the  opinions  of  others  be 
formed  independently  of  my  own,  I  will  defer  de- 
scribing them  until  another  paper,  merely  stating 
that  there  is  some  evidence  that  certain  regions  do 
not  seem  to  remain  at  all  times  of  the  same  color. 

In  closing,  I  shall  mention  that  these  colors  have 
been  seen  through  three  different  telescopes,  12-inch 
and  15-inch  at  Cambridge,  and  more  recently 
through  the  13-inch  instrument  at  Arequipa.  The 


Colors  Exhibited  by  the  Planet  Mars        35 

latter  instrument  brought  them  out  very  finely,  the 
greens  showing  well  even  in  the  day-time.  On  April  5, 
I  could  see  the  great  canal  north  of  the  Syrtis  Major 
with  a  power  of  810  diameters.  It  will  be  noted 
that  in  what  precedes  I  have  carefully  abstained 
from  advocating  any  hypothesis  regarding  the  true 
sources  of  any  of  the  colors,  merely  confining  myself 
strictly  to  a  statement  of  the  observed  facts. 

In  my  former  paper  upon  this  subject,  attention 
was  called  to  the  important  effect  of  our  own  at- 
mosphere in  misleading  our  judgment  as  to  the  true 
colors  exhibited  by  the  heavenly  bodies.  A  good 
illustration  of  this  effect  may  be  obtained  from  a 
mountain  summit  upon  a  slightly  cloudy  day.  The 
distant  greens  of  the  landscape,  which  are  by  no 
means  as  brilliant  as  when  viewed  close  at  hand,  are 
at  once  changed  to  grays  either  by  the  passing  over 
them  of  a  cloud  shadow,  or  by  the  passing  of  a  very 
thin  mist  between  them  and  the  eye.  In  the  former 
they  become  darker,  and  in  the  latter  lighter,  but 
in  either  case  the  greenish  tint  entirely  disappears. 

The  sudden  changes  of  color  exhibited  by  some 
of  the  smaller  areas  upon  the  planet  Mars  are  some- 
times almost  startling.  A  recent  view  was  obtained 
shortly  before  sunrise,  when  the  snowy  region  about 
the  south  pole  appeared  of  a  most  brilliant  green, 
quite  equalling  in  color  the  rather  narrow  green 
band  situated  just  to  the  north  of  it.  Later  as  the 


36  Mars 

Sun  came  up,  the  color  of  the  snow  changed  to  bright 
yellow,  the  rest  of  the  disc  changing  in  the  mean 
time  to  orange.  Later  the  seeing  improved,  several 
of  the  canals  became  visible,  and  the  snow  became  as 
colorless  as  that  upon  our  surrounding  mountains. 
The  two  former  effects  were  probably  due  to  bad 
seeing,  the  fluctuations  of  our  own  atmosphere  super- 
posing the  colors  of  the  surrounding  regions  upon 
the  snow.  We  have  laid  it  down  as  a  rule  never  to 
rely  greatly  upon  our  color  observations  unless  the 
snow  caps  of  the  planet  appear  perfectly  colorless, 
and  the  canal  system  is  well  defined.  These  condi- 
tions we  find  always  combined  with  the  best  seeing. 
For  these  delicate  color  observations  it  will  therefore 
be  seen,  that  not  only  do  we  require  a  telescope  of 
the  very  first  quality,  but  also  the  very  best  obtain- 
able atmospheric  conditions. 

In  studying  the  smaller  dark  regions,  such  as 
the  northwestern  part  of  the  Syrtis  Major,  great 
differences  of  color  have  been  noted  from  night  to 
night,  and  I  have  colored  sketches  in  my  possession, 
taken  at  different  times,  in  which  it  is  represented 
as  grey,  as  green,  as  blue,  as  brown  and  even  as 
violet.  The  latter  color  was  so  extraordinary  that  I 
endeavored  to  make  that  portion  of  the  planet  ap- 
pear to  my  eye  of  some  other  color,  but  it  was 
impossible,  and  no  other  color  but  violet  lake  could 
be  made  to  match  it.  This  color  upon  the  planet 


Colors  Exhibited  by  the  Planet  Mars        37 

has  only  been  seen  by  me  upon  one  occasion  since. 
The  brown  color  above  noted  was  undoubtedly  due 
to  bad  seeing.  At  one  time  I  felt  convinced  that 
the  real  color  of  the  darkest  spots  upon  the  planet 
was  a  deep  blue,  and  this  may  in  reality  be  the  case, 
but  of  late,  under  the  most  favorable  circumstances, 
they  have  appeared  to  me  of  an  absolutely  colorless 
dark  grey.  Probably  this  point  can  be  settled  at 
the  present  opposition. 

Before  describing  the  colors  of  particular  regions 
more  at  length,  it  may  be  well  to  give  a  description 
of  the  general  characteristics  of  different  longitudes, 
as  observed  during  the  opposition  of  1890.  For  this 
purpose  we  may  divide  the  surface  of  the  planet 
into  six  sections,  each  sixty  degrees  of  longitude  in 
breadth,  the  first  having  the  0°  meridian  central. 
The  times  of  transit  of  the  0°  meridian  of  the  planet 
may  be  readily  computed,  but  the  amateur  will  find 
them  given  in  convenient  shape  in  the  excellent 
ephemerides  published  by  Mr.  Marth  in  the  Monthly 
Notices.  The  only  pity  is  that  these  ephemerides 
cannot  appear  about  six  months  earlier,  in  order  to 
be  of  the  most  use  to  astronomers  outside  of  the 
British  Islands. 

The  most  striking  marking  upon  the  planet,  and 
that  most  readily  seen  with  a  small  telescope,  is  the 
Syrtis  Major,  or  Y  mark.  This  is  nearly  central 
in  the  sixth  position  of  the  planet,  with  the  300° 


38  Mars 

meridian  in  the  middle  of  the  disc.  Owing  to  the 
period  of  rotation  of  Mars  being  37  minutes  longer 
than  that  of  the  Earth,  in  about  six  nights  Mars 
will  be  found  at  the  same  hour  in  the  fifth  position 
with  the  240°  meridian  central.  This  region  in  1890 
was  interesting  as  containing  the  most  conspicuous 
canals  visible  upon  the  planet,  excepting  the  large 
one  which  terminates  the  Syrtis  Major  upon  the 
north.  At  this  opposition  these  canals  will  all  be 
too  far  north  to  be  well  seen.  The  fourth  and  third 
regions  of  the  planet  were  both  extremely  uninterest- 
ing as  showing  very  little  detail  of  consequence. 
The  second  position  with  the  60°  meridian  central 
was  interesting  as  showing  the  great  southern  ocean, 
which  is  nearly  as  conspicuous  as  the  Syrtis  Major 
itself.  In  the  first  position  with  the  0°  meridian 
central  the  ocean  is  disappearing  and  the  Syrtis 
Major  coming  into  view. 

We  now  come  to  a  curious  feature  of  the  observa- 
tions, namely,  the  actual  changes  in  color  which, 
eliminating  all  probable  sources  of  error,  the  sur- 
face of  the  planet  really  seems  to  undergo.  When 
the  Syrtis  Major  is  central,  before  the  autumnal 
equinox  of  the  northern  hemisphere,  the  region  to  the 
east  is  seen  to  be  distinctly  more  greenish  than  that 
to  the  west.  As  the  season  wears  on  the  difference 
in  color  becomes  less  marked,  and  the  greenish  hue 
is  confined  more  closely  to  the  region  immediately 


Colors  Exhibited  by  the  Planet  Mars        89 

bordering  the  Syrtis  on  the  east.  In  most  of  my 
drawings  made  in  1890  the  two  arms  of  the  Syrtis 
are  shown  of  equal  breadth.  This  appears  to  be 
the  case  also  upon  Green's  map  published  in  Cham- 
bers' Astronomy,  although  this  point  is  not  well 
shown  by  him.  At  present  there  is  no  doubt  but  that 
the  eastern  arm  is  much  the  wider  of  the  two,  per- 
haps twice  as  wide.  Early  in  1890  the  entire  region 
enclosed  between  the  arms  of  the  Syrtis  Major,  as 
far  as  the  snow  cap,  was  of  a  brilliant  green  color. 
On  June  27,  however,  or  eleven  days  before  the 
vernal  equinox  of  the  southern  hemisphere,  a  yellow 
spot  appeared  at  the  extreme  northern  point  of  the 
triangular  area.  As  the  season  advanced  this  yellow 
spot  increased  in  area,  till  it  covered  the  whole 
region  as  far  south  as  could  be  seen.  This  year  when 
first  observed,  this  area  was  entirely  green,  but  on 
May  9,  or  seventeen  days  before  the  vernal  equinox, 
the  yellow  or  perhaps  reddish  spot  appeared  in  the 
same  place,  and  it  will  be  interesting  to  determine 
if,  as  the  season  advances,  this  color  again  pro- 
gresses towards  the  pole.  Changes  to  the  east  of 
the  Syrtis  Major  have  also  been  noticed  by  Schi- 
aparelli.  These  he  ascribes  to  extensive  floods.  On 
June  8,  1890,  thirty  days  before  the  autumnal  equi- 
nox in  the  northern  hemisphere,  there  was  a  large 
greenish  area  visible  in  longitude  180°,  latitude  80° 
north.  By  July  16,  or  eight  days  after  the  equinox, 


40  Mars 

this  spot  could  not  be  found,  the  whole  region  ap- 
pearing of  a  yellow  tint.  In  longitude  10°,  latitude 
40°  north,  is  a  large  crescent-shaped  area.  In  June 
and  July,  1890,  it  was  well  seen  and  appeared  quite 
as  dark  as  the  great  southern  ocean.  This  was  noted 
upon  a  number  of  occasions.  It  was  however  painted 
green,  and  the  ocean  to  the  south  of  it  blue,  the 
difference  in  color  on  one  evening  being  very  clear, 
as  seen  by  my  assistant,  Mr.  A.  E.  Douglass,  and 
myself.  On  March  22  of  the  present  year  the  cres- 
cent was  well  shown,  but  was  markedly  fainter  than 
the  ocean,  which  was  again  suspected  of  being  blue, 
but  the  color  could  not  be  satisfactorily  confirmed. 
This  crescent  is  now  too  far  north,  owing  to  the 
motion  of  the  planet,  to  be  satisfactorily  studied. 

While  these  indications  of  change  of  color  upon 
the  planet  are  too  few  and  isolated  at  present  to 
enable  us  to  form  a  satisfactory  explanation  of  their 
causes,  they  still  hold  out  a  promise  that  should 
these  observations  be  carefully  repeated  at  future 
oppositions,  under  suitable  conditions,  we  may  in 
time  be  able  to  deduce  the  laws  affecting  them,  and 
perhaps  even  predict  their  changes  in  advance.  Too 
much  stress  however  cannot  be  laid  on  the  danger 
of  optical  illusion  in  this  matter.  It  is  generally 
considered  that  a  very  good  instrument,  and  some 
practice  is  required,  before  an  observer  can  cer- 


Colors  Exhibited  by  the  Planet  Mars        41 

tainly  see  the  canals  even,  but  in  order  that  satis- 
factory results  in  this  branch  of  the  research  may 
be  achieved,  the  more  important  canals  must  be  seen 
with  distinctness,  and  the  snow  caps,  if  present, 
must  appear  perfectly  colorless. 


CHAPTER    V 
CHANGES  AND  FLOODS  ON  MARS1 

In  the  previous  chapter  an  endeavor  was  made  to 
show  that  actual  changes  do  occur  upon  its  sur- 
face, besides  the  well  known  annual  change  in  the 
size  of  the  snow  caps.  This  effort  has  perhaps 
proved  unnecessary  since  the  changes  which  have 
actually  occurred  at  the  present  opposition  have 
been  so  conspicuous  and  startling  that  they  might 
easily  be  detected  even  by  the  possessors  of  six-inch 
telescopes.  The  canals  can  now  be  observed  read- 
ily any  evening.  Many  of  those  that  we  have  seen 
here  agree  with  Schiaparelli's,  and  several  do  not. 
Several  of  his  more  strongly  marked  ones  have  not 
been  found  at  all.  This,  however,  I  am  quite  pre- 
pared to  attribute  to  seasonal  changes.  Some  very 
well  developed  canals  cross  the  oceans.  If  these  are 
really  water  canals  and  water  oceans,  there  would 
seem  to  be  some  incongruity  here.  When  the  snow 
melts,  it  seems  that  there  really  should  be  some 
oceans,  and  a  careful  study  has  been  made  of  the 

1  Astronomy  and  Astro-Physics,  1892,  11,  668. 
42 


Changes  and  Floods  on  Mars  45 

dark  spot  previously  referred  to,  at  the  northern 
end  of  the  Syrtis  Major.  Although  sometimes  dark 
gray,  yet  in  the  great  majority  of  cases  when  the 
seeing  is  satisfactory,  and  the  spot  is  central,  it 
appears  of  a  clearly  defined  dark  blue  color.  An- 
other spot  presenting  a  precisely  similar  appearance* 
occupies  a  portion  of  the  Sinus  Sabaeus  or  Herschel 
Strait. 

These  two  spots  when  near  the  limb  have  on  sev- 
eral occasions  been  observed  to  be  of  a  beautiful 
bright  blue  color.  If  they  are  really  oceans,  they 
must,  under  these  circumstances,  be  reflecting  to  our 
eyes  the  color  of  the  Arean  atmosphere,  as  water 
would,  under  similar  conditions,  do  upon  our  Earth. 

Viewed  with  a  double  image  prism  these  spots 
when  near  the  limb  seem  to  present  faint  traces  of 
polarization,  the  plane  being  radial  to  the  planet. 
Until  very  recently  they  were  much  darker  than  any 
other  spots  visible,  although  a  dark  region  near 
Solis  Lacus  (Terby  Sea)  has  upon  one  occasion  ap- 
peared quite  black.  It  is  my  impression  that  these 
two  areas  are  really  water,  and  in  the  present  arti- 
cle they  will  be  referred  to  provisionally  as  the 
Northern  and  Equatorial  Seas  respectively.  As  I 
have  stated  in  former  articles  I  very  much  doubt 
if  what  are  usually  known  as  oceans  and  canals  con- 
tain any  water  at  all.  That  is  to  say,  any  water 
which  is  visible  as  such,  for  it  is  quite  possible  and 


44  Mars 

perhaps  probable  that  they  may  owe  this  color  in- 
directly to  the  presence  of  water,  stationary  or  run- 
ning. 

The  boundaries  of  the  Equatorial  Sea  (Fig.  2) 
are  all  sharply  defined.  It  is  1,300  miles  in  length, 
east  and  west,  and  averages  a  trifle  over  200  miles 
in  breadth,  with  two  deep  bays  slightly  curved,  and 
almost  precisely  alike,  opening  southward,  at  its 
western  end.  In  this  article  I  have  adopted  the 
precedent  set  by  Professor  Schiaparelli  in  applying 
the  terms  east  and  west  with  the  same  signification 
as  is  given  to  them  in  maps  of  the  Earth.  That  is 
they  are  reversed  as  compared  with  other  celestial 
maps.  Its  total  area  is  275,000  square  miles.  The 
shape  of  the  Northern  Sea  (Fig.  3)  is  that  of  an 
irregular  quadrilateral,  750  miles  in  length  by  600 
in  breadth.  On  the  north  its  outlines  are  as  clearly 
defined  as  those  of  the  other  sea,  but  on  the  south 
it  is  bounded  by  a  dark  gray  region,  never  seen 
hitherto  to  be  blue  and  which  I  am  inclined  to 
ascribe  for  reasons  which  will  appear  later  to  low 
land.  If  its  shores  were  indented,  this  might  ac- 
count for  their  rather  indistinct  appearance.  Its 
area  is  nearly  equal  to  that  of  the  Equatorial  Sea, 
being  approximately  225,000  square  miles.  What 
we  may  therefore  speak  of  as  the  permanent  water 
area  upon  Mars  amounts  to  about  half  a  million 
square  miles.  This  is  exactly  one-half  the  area  of 


Changes  cmd  Floods  on  Mars  45 

the  Mediterranean  Sea.  A  glance  at  the  map  of  the 
world  in  two  hemispheres  will  give  the  reader  an  idea 
of  the  enormous  disparity  in  the  water  area  of  the 
two  planets.  From  this  circumstance  we  might  ex- 
pect the  climate  of  the  smaller  planet  to  be  on  the 
whole  much  the  dryer  of  the  two,  and  if  all  is  not 
a  desert,  at  least  that  the  deserts  would  be  much 
more  prominent  than  upon  the  Earth. 

In  this  connection  we  may  refer  to  the  green 
areas  situated  near  the  poles,  and  described  at  some 
considerable  length  in  the  previous  chapter.  It 
was  there  stated  that  after  the  vernal  equinox  the 
greens  almost  entirely  disappeared  and  the  ques- 
tion was  raised  whether  the  same  effect  would  be 
noticed  this  year.  We  can  now  reply  in  the  af- 
firmative, for  although  we  have  searched  for  them 
with  the  utmost  care  of  late,  when  the  seeing  was 
both  better  and  worse  than  before,  scarcely  a  trace 
of  them  have  we  been  able  to  detect.  There  is  also 
a  green  area  to  the  west  of  the  Equatorial  Ocean, 
but  this  region  we  have  not  been  able  to  inspect  care- 
fully of  late.  In  case  they  should  reappear  before 
the  present  opposition  is  over,  as  is  possible,  it  is 
hoped  that  others  will  be  upon  the  watch  to  detect 
them,  and  accurately  locate  their  positions.  While 
their  reappearance  might  with  some  show  of  prob- 
ability be  attributed  to  the  presence  of  one  of  the 
great  branches  of  organic  life  upon  the  planet, 


46  Mars 

and  with  this  branch,  as  an  almost  necessary  corol- 
lary, the  other  one,  we  must  still  consider  the  mat- 
ter merely  in  the  light  of  a  tentative  hypothesis, 
until  further  observations  are  accumulated,  and 
content  ourselves  with  the  statement  that  no  facts 
have  as  yet  been  observed  inimical  to  this  idea.  The 
one  fact  which  we  have  so  far  attempted  to  demon- 
strate is  the  presence  upon  the  planet  of  water  in 
the  liquid  form,  and  the  attempt  has  been  made  to 
determine  its  exact  location,  and  the  area  and  shape 
of  the  surfaces  permanently  covered  by  it. 

As  might  have  been  expected  from  the  position 
of  the  planet's  axis,  the  snow  cap  is  much  more 
conspicuous  at  this  opposition  than  it  was  at  the 
last.  On  June  23,  the  northern  limit  of  the  south- 
ern polar  snow  cap  was,  on  the  average,  in  latitude 
— 65°.  This  in  our  northern  hemisphere  would 
correspond  to  the  latitude  of  northern  Siberia,  Ice- 
land, and  northern  British  America.  As  this  date 
was  but  thirty  days  after  the  passage  of  the  vernal 
equinox,  it  will  be  seen  that  the  line  of  melting 
snow  was  rather  nearer  the  pole  than  we^might  ex- 
pect to  find  it  upon  our  own  Earth  at  the  same 
period.  The  area  of  this  snow  cap  was  some  2,400,- 
000  square  miles.  Upon  this  date  a  small  dark  spot 
was  noted  near  the  center  of  the  snow.  The  spot 
was  then  well  developed,  and  must  have  been  already 
existing  for  several  days.  Since  that  time  it  has 


Changes  and  Floods  on  Mars  47 

grown  rapidly,  soon  splitting  the  snow  cap  into  two 
unequal  parts,  and  of  late  changing  its  shape  ma- 
terially. The  snow  cap  in  the  meantime  has  rap- 
idly diminished  in  size,  so  rapidly  in  fact,  that  con- 
sidering the  weakened  power  of  the  sunlight  at  that 
distance,  we  are  forced  to  believe  that  its  depth  is 
much  less  than  that  of  the  similar  deposit  covering 
the  poles  of  our  Earth.  It  will  thus  be  seen  that 
the  comparatively  small  snow  caps  of  Mars  by  no 
means  necessarily  imply  a  warmer  climate  than  that 
of  the  Earth,  as  some  writers  have  assumed,  but 
merely  a  drier  one.  If  the  snow  fell  to  a  less  depth, 
a  larger  proportion  of  the  heat  absorbed  in  the 
higher  latitudes  could  be  employed  in  raising  the 
temperature,  and  a  less  amount  absorbed  in  the  lat- 
ent form.  This  would  involve  a  somewhat  higher 
temperature  during  the  summer,  but  a  longer  period 
of  intense  cold  during  the  winter,  than  exists  upon 
the  Earth,  in  proportion  to  the  length  of  the  year. 

Upon  July  26  it  was  found  that  the  area  of  the 
snow  cap  had  diminished  to  800,000  square  miles. 
An  area  of  1  $00,000  square  miles  of  snow  had, 
therefore,  been  converted  into  water,  in  the  space  of 
thirty-three  days.  With  our  extensive  oceans  this 
would  produce  no  material  change  upon  the  Earth, 
but  what  must  be  the  effect  upon  Mars,  whose  total 
permanent  water  area  amounts  to  less  than  one- 
third  of  this  figure?  Moreover,  upon  the  Earth  the 


48  Mart 

semi-annual  transfer  of  the  melted  snow  from  pole 
to  pole  is  conducted  by  means  of  the  oceans,  but 
upon  Mars  this  transfer  must  take  place  across  the 
land.  We  should  naturally  expect  that  a  consider- 
able proportion  of  the  water  would  be  absorbed  or 
deposited  upon  the  way.  It  will  therefore  be  in- 
teresting to  notice  what  has  actually  been  observed. 
Eastward  of  the  stem  of  the  Y*,  in  what  is  known 
as  Libya,  there  was  observed  by  Mr.  A.  E.  Douglass 
upon  May  8,  and  by  myself  quite  independently, 
upon  May  9,  a  light  colored  triangular  region  with 
a  bright  triangular  center  (Fig.  1).  The  angles  of 
the  central  region  were  so  distinct  that  they  were 
selected  as  stations  for  our  micrometric  survey  of 
the  surface.  At  the  next  presentation  of  this  phase, 
a  month  later,  the  central  triangle  had  entirely  van- 
ished, being  of  the  same  tint  as  the  outer  triangular 
area,  thus  rendering  it  quite  impossible  to  employ 
the  selected  stations.  The  whole  area  was,  however, 
still  much  lighter  than  the  stem  of  the  Y.  June  11, 
it  had  a  decidedly  greenish  gray  tint  when  central, 
and  two  days  later  it  had  assumed  the  same  gray 
color  as  the  stem  of  the  Y  from  which  it  was  indis- 
tinguishable. July  17,  that  portion  of  this  region 
south-east  of  the  Northern  Sea  had  become  extremely 
dark  (Fig.  4),  being  only  exceeded  in  tint  by  the 
sea  itself,  which  differed  from  it  mainly  in  color,  the 
sea  being  blue  and  this  region  gray. 
*  The  Syrtis  Major. 


FIG.  1 
May  9,  21h  05m 


FIG.  2 
July  14,  16h  50m 


FIG.  3 
July  16,  17b  45m 


FIG.  4 
July  17,  15h  50m 


FIG.  5 
July  23,  17h  30m 


FIG.  6 
July  25,  20h  40m 


Note  in  Regard  to  the  Figures.  In  the  above  figures  north 
is  placed  at  the  top.  The  date  is  given  in  Greenwich  Mean 
Time.  The  scale  is  200  kilometers  (125  miles)  to  the  milli- 
meter. In  the  last  five  figures  1"  =  1.4  millimeters. 

49 


50  Mart 

Upon  July  10,  the  region  south-west  of  the  Equa- 
torial Sea  was  extremely  faint,  and  but  little  darker 
than  the  reddish  region  to  the  north  of  it.  A  simi- 
lar effect  had  been  suspected  in  June.  This  seems 
the  more  singular,  since  after  the  Seas  this  is  usually 
one  of  the  very  darkest  and  most  conspicuous  mark- 
ings upon  the  planet.  The  region  west  of  this  has 
also  been  subject  to  various  changes,  which  need  not, 
however,  be  described  in  the  present  article. 

Upon  May  12,  it  was  noticed  that  the  southern 
snow  cap  was  bounded  by  a  very  fine  black  line.  By 
June  23  this  had  become  quite  conspicuous  in  some 
places.  By  July  10,  that  portion  of  the  line  lying 
upon  the  Arean  meridian  was  as  dark  as  the  Equa- 
torial Sea,  and  appeared  quite  like  it.  On  July  16, 
a  small  elongated  black  spot  was  noticed  upon  the 
western  side  of  the  stem  of  the  Y  (Fig.  3).  It  was 
then  so  conspicuous,  that  I  was  surprised  I  had  not 
noticed  it  before.  My  measurements  indicated  that 
it  was  about  125  miles  in  length  by  75  miles  in 
breadth.  This  would  make  it  of  about  the  same  size 
as  Lake  Erie,  and  it  was  connected  with  the  North- 
ern Sea  by  a  very  narrow  straight  black  line.  This 
line  did  not  at  all  resemble  the  so-called  canals,  be- 
ing much  finer  and  blacker.  This  spot  was  again 
seen  by  myself  upon  July  17,  and  by  Mr.  Douglass 
upon  July  22,  after  which  it  disappeared  unex- 
pectedly in  a  way  which  I  shall  presently  relate. 


Changes  and  Floods  on  Mars  51 

Changes  were  now  coming  thick  and  fast  upon  the 
planet,  and  when  evening  came  round,  and  we  put 
our  eyes  to  the  telescope,  we  never  knew  what  we 
should  see  next.  In  my  August  paper  reference  is 
made  among  other  suspected  changes  to  the  two 
arms  of  the  Y,  which  in  the  opposition  of  1890  were 
always  drawn  of  approximately  equal  width.  The 
statement  was  then  made:  "At  present  there  is  no 
doubt  but  that  the  eastern  arm  is  much  the  wider 
of  the  two,  perhaps  twice  as  wide."  This  paper  was 
completed  May  13,  1892.  This  statement  still  re- 
mained true  upon  June  10  and  11,  but  at  the  next 
presentation  upon  July  12,  a  central  arm  was  shown, 
converting  the  Y  into  a  trident.  This  arm  connected 
directly  with  the  dark  streak  or  split  in  the  snow 
cap  (Fig.  2).  The  eastern  arm  was  still  much  the 
widest,  but  in  two  days  the  difference  between  it  and 
the  western  was  much  less  marked,  and  by  July  17, 
they  were  equal  in  breadth,  just  as  they  appeared 
in  1890  (Fig.  4).  In  the  meantime  the  central  arm 
of  the  trident  had  become  much  more  prominent, 
being  about  equally  conspicuous  with  the  other  two, 
and  now,  to  my  astonishment  was  seen  a  large  dark 
area  south-east  of  the  Northern  Sea  and  of  fully 
double  its  area.  This  dark  region  is  the  one  re- 
ferred to  earlier  in  this  paper  as  having  formerly 
been  very  light  colored.  It  was  now  nearly  as  dark 
as  the  Sea,  and  much  darker  than  that  part  of  the 


58  Mart 

Y  to  the  south  of  it.  In  color  it  was  gray,  and  not 
blue.  This  observation  was  independently  confirmed 
by  Mr.  Douglass  the  next  evening.  By  July  £3,  this 
darkening  had  greatly  diminished,  the  color  of  the 
dark  region  being  of  the  same  depth  as  that  of  the 
rest  of  the  Y  (Fig.  5),  which  latter  had  now  mate- 
rially changed  its  shape,  owing  to  eastward  exten- 
sions of  the  eastern  arm.  In  the  meantime  the  cen- 
tral arm,  recently  so  strongly  marked,  had  com- 
pletely disappeared.  But  what  was  most  extraordi- 
nary was  that  the  Northern  Sea  had  now  extended 
far  to  the  south-west,  completely  concealing  the  lit- 
tle lake  and  the  channel  connecting  the  two.  This 
result  was  also  confirmed  independently  by  Mr. 
Douglass  the  next  evening.  By  "independently"  I 
mean  that  he  made  his  drawing  without  having  seen 
mine,  or  knowing  at  all  what  I  had  seen.  Indeed, 
both  of  us  were  doing  so  much  observing  at  this  time 
that  we  had  little  opportunity  to  compare  results, 
and,  unfortunately,  did  not  fully  appreciate  the  ex- 
tent of  the  changes  we  were  observing,  and  so  de- 
voted a  considerable  share  of  our  attention  to  other 
matters.  This  will  account  for  the  apparent  breaks 
in  this  record,  for,  with  the  exception  of  July  9, 
when  some  repairs  were  being  made  upon  the  tele- 
scope, continuous  observations  have  been  main- 
tained since  July  4. 

To  return  to  the  observations,  it  is  not  clear  from 


Changes  and  Floods  on  Mars  53 

the  record  whether  the  southern  extension  of  the 
Northern  Sea  was  blue  or  gray.  It  was  merely  re- 
corded and  drawn  "as  dark  as  the  Northern  Sea." 
On  July  24  Mr.  Douglass  also  recorded  a  large 
southern  dark  spot  which  appeared  to  him  as  dark  as 
the  Northern  Sea,  but  which  I  had  not  noticed  upon 
the  23d.  Upon  July  25  the  original  outlines  of  the 
Northern  Sea  were  again  well  seen  (Fig.  6),  the  re- 
gion south-west  of  it  now  being  much  lighter  colored. 
The  southern  dark  area  seen  by  Mr.  Douglass,  and 
of  which  he  had  told  me,  was  also  noted.  As  a  whole 
this  area  was  not  now  as  dark  as  the  Northern  Sea, 
but  it  contained  a  smaller  spot  which  seemed  quite 
as  dark.  There  was  also  a  narrow  white  channel 
extending  northwards  from  the  snow.  The  eastern 
arm  of  the  Y,  formerly  so  wide,  was  now  reduced  to 
a  mere  thread,  while  a  trace  of  the  central  arm  was 
again  visible. 

The  Y  is  now  so  placed  that  it  is  only  visible  to 
the  observatories  to  the  west  of  us,  and  we  shall  not 
be  able  to  observe  it  again  until  the  middle  of  Au- 
gust. A  striking  difference  may  be  noted  in  the  ar- 
rangement of  the  dark  channels  in  figures  3  and  4. 
In  both  instances  they  were  well  seen,  and  carefully 
drawn,  and  I  do  not  see  how  the  difference  could  be 
due  to  an  error.  The  latter  arrangement  was  sub- 
sequently confirmed  by  two  other  drawings.  Re- 
garding the  former  I  find  the  record,  "The  dark 


54  Mars 

parts  are  usually  not  more  than  150  miles  broad." 
I  can  scarcely  think,  however,  that  they  could  have 
been  as  broad  as  that. 

The  central  branch  of  the  Y  was  only  noted  by 
me  upon  one  occasion  in  1890,  and  that  was  upon 
May  25,  when  it  was  extremely  faint.  The  date  cor- 
responding to  July  12,  1892,  in  the  previous  opposi- 
tion was  August  24,  1890.  At  that  time  the  Y  was 
not  visible  in  Cambridge.  The  corresponding  date 
at  the  next  opposition  will  be  May  31,  1894.  If  the 
appearance  of  this  central  branch  is  in  any  way 
connected  with  the  seasons  upon  Mars,  it  will  be  of 
interest  for  those  observatories  which  are  favorably 
situated  at  that  time  to  look  for  it,  since,  should  it 
then  be  as  conspicuous  a  phenomenon  as  it  has  been 
this  year,  it  could  be  readily  detected  by  compara- 
tively small  telescopes. 

In  seeking  to  explain  these  observations,  I  would 
merely  point  out  the  fact  that  the  changes  occurred 
at  a  time  when  the  snow  was  melting  with  great 
rapidity,  that  a  dark  channel  suddenly  appeared 
July  12,  which  had  not  been  seen  at  the  last  pre- 
vious observation  of  this  region  June  13,  that  it 
shortly  disappeared  again,  and  that  a  few  days 
after  this  event  the  Northern  Sea  largely  increased 
in  area  temporarily,  or  at  least  that  its  southern 
shores  became  much  darker.  I  think  these  changes 
cannot  be  explained  by  Arean  cloud  effects.  We 


Changes  and  Floods  on  Mars  55 

have  already  observed  large  whitish  patches  upon 
the  planet,  which  undergo  considerable  changes  in 
shape  and  extent  from  night  to  night.  We  are  now 
studying  them  carefully,  although  we  find  them 
rather  difficult  of  observation.  These  changes  we 
are  inclined  to  refer  to  clouds,  although  the  matter 
is  not  so  simple  as  it  might  at  first  appear.  If 
these  effects  are  really  due  to  clouds,  they  are  quite 
different  in  character  from  the  other  changes  noted 
above. 

If  the  reader  is  inclined  to  be  surprised  at  the 
extraordinary  character  of  the  phenomena  now  ap- 
parently occurring  upon  our  sister  planet,  as  re- 
vealed by  the  telescope,  I  can  assure  him  that  he  is 
no  more  so  than  were  the  observers  themselves.  Nor 
do  we  insist  upon  any  explanation  of  these  changes, 
but  only  upon  the  accuracy  of  the  observations  them- 
selves. Owing  to  our  remote  and  isolated  position, 
we  know  nothing  at  the  present  writing  of  what  has 
been  done  and  seen  at  the  northern  Observatories, 
and  it  is  possible  that  when  this  strikes  the  reader's 
eye,  it  will  not  be  as  new  to  him  as  it  is  now  to  us. 
Nevertheless,  I  am  inclined  to  think  that  owing  to 
our  splendid  atmosphere,  and  southern  latitude,  por- 
tions of  what  precedes  may  still  be  new,  although 
the  larger  northern  telescopes  will  doubtless  have 
detected  all  the  more  important  changes. 


CHAPTER    VI 
MARS  IN  1892  * 

Now  that  the  opposition  of  189&  has  passed  into 
history,  it  may  be  well  to  give  a  brief  summary  of 
the  observations  made  at  Arequipa  this  year,  pre- 
paratory to  a  more  complete  publication  elsewhere. 
With  one  exception,  the  planet  has  been  observed 
every  night  continuously,  from  July  9  until  Septem- 
ber 24,  when  the  lens  of  the  telescope  was  reversed, 
for  photographic  work,  and  the  regular  observations 
came  to  an  end.  Since  the  beginning  of  the  year 
Mr.  Douglass  and  myself  have  made  373  drawings 
of  different  features  of  the  planet,  thirteen  of  them 
being  colored.  Numerous  micrometric  measure- 
ments of  the  equatorial,  polar,  and  phase  diameters 
have  been  made.  A  large  number  of  measurements 
of  the  snow,  and  other  observations  for  correcting 
the  physical  ephemeris  of  the  planet  have  been  col- 
lected. Ninety-two  stations  have  been  located  upon 
the  planet  micrometrically,  many  of  them  having 
been  observed  upon  several  different  dates.  Besides 

1  Astronomy  and  Astro-Physics,  1892,  11,  849. 

66 


Mars  m  1892  57 

these,  measurements  of  the  clouds,  and  the  breadths 
of  the  lakes,  canals,  and  minor  features  have  been  ob- 
tained. Considerable  data  has  thus  been  collected 
at  this  opposition  for  future  discussion. 

Turning  now  to  what  we  may  call  the  definite 
conclusions  to  be  derived  from  our  observations,  we 
may  say: — 

I.  That  the  polar  caps  are  clearly  distinct  in  ap- 
pearance from  the  cloud  formations,  and  are  not  to 
be  confounded  with  them. 

II.  That  clouds  undoubtedly  exist  upon  the  planet, 
differing,  however,  in  some  respects  from  those  upon 
the  Earth,  chiefly  as  regards  their  density  and  white- 
ness. 

III.  There  are  two  permanently  dark  regions  upon 
the  planet,  which  under  favorable  circumstances  ap- 
pear blue,  and  are  presumably  due  to  water. 

IV.  Certain  other  portions  of  the  surface  of  the 
planet  are  undoubtedly  subject  to  gradual  changes 
of  color,  not  to  be  explained  by  clouds. 

V.  Excepting  the  two  very  dark  regions  referred 
to  above,  all  of  the  shaded  regions  upon  the  planet 
have  at  times  a  greenish  tint.     At  other  times  they 
appear  absolutely  colorless.     Clearly  marked  green 
regions  are  sometimes  seen  near  the  poles. 

VI.  Numerous    so-called    canals    exist    upon    the 
planet,  substantially  as  drawn  by  Professor  Schia- 
parelli.      Some   of   them   are   only   a   few  miles   in 


58  Mars 

breadth.     No  striking  instances  of  duplication  have 
been  seen  at  this  opposition. 

VII.  Through    the    shaded    regions    run    certain 
curved  branching  dark  lines.     They   are  too   wide 
for  rivers,  but  may  indicate  their  courses. 

VIII.  Scattered  over  the  surface  of  the  planet, 
chiefly  on  the  side  opposite  to  the  two  seas,  we  have 
found  a  large  number  of  minute  black  points.     They 
occur  almost  without  exception  at  the  junctions  of 
the  canals  with  one  another,  and  with  the  shaded 
portions  of  the  planet.     They  range  from  thirty  to 
one  hundred  miles  in   diameter,  and  in  some  cases 
are  smaller  than  the  canals  in  which  they  are  sit- 
uated.   Over  forty  of  them  have  been  discovered,  and 
for  convenience  we  have  termed  them  lakes. 

No  repetition  of  the  phenomena  connected  with 
the  melting  snow,  which  occurred  in  July  has  been 
observed.  The  Y  mark  has  assumed  its  customary 
appearance,  so  that  the  narrowing  of  the  southern 
branch  seems  to  have  been  a  temporary  phenom- 
enon, and  was  probably  due  to  clouds.  The  central 
branch  is  now  continuously  visible,  but  its  southern 
extremity  which  connected  it  with  the  snow  has  dis- 
appeared. The  southern  branch  of  the  Y  also  seems 
to  be  gradually  fading  out. 

Clouds  have  on  several  occasions  been  observed  to 
project  beyond  the  terminator,  and  also  beyond  the 
limb,  thus  confirming  the  observations  made  at  the 


Mars  m  1892  59 

Lick  Observatory.  The  height  of  these  clouds  has 
been  measured,  and  it  appears  that  some  of  them 
attained  an  altitude  of  at  least  twenty  miles, — a 
height  considerably  greater  than  that  attained  by 
terrestrial  clouds.  This  is  a  result  naturally  to  be 
expected  from  the  small  mass  of  the  planet.  No 
direct  measures  have  been  possible  of  the  density 
of  the  atmosphere  at  the  planet's  surface,  but  in- 
direct observations  lead  us  to  conclude  that  it  is 
less  than  that  at  the  surface  of  the  Earth,  but  prob- 
ably not  as  much  as  ten  times  less. 

A  curious  feature  of  the  observations  has  been  the 
distinct  flattening  at  the  planet's  poles,  amounting 
to  at  least  ^.  From  theoretical  considerations, 
unless  we  assume  a  rather  improbable  internal  struc- 
ture, it  cannot  exceed  ^Q,  and  that  is  approxi- 
mately the  figure  which  Professor  Young  derived 
from  his  measurements.  Herschel  made  it  ^, 
Arago  i,  and  other  observers  have  obtained  vari- 
ous results,  in  general  greater  than  ours.  The  above 
figure  must  not  be  considered  by  any  means  final, 
but  merely  as  an  approximate  minimum,  since  our 
computations  have  not  as  yet  been  completed.  That 
the  flattening  at  opposition  was  considerable  was 
very  evident.  As  no  such  conspicuous  discrepancies 
among  different  observers  occur  in  the  case  of  the 
other  planets,  I  am  inclined  to  think  that  the  varia- 
tions may  be  real,  and  due  perhaps  to  an  equatorial 


60  Mars 

cloud  formation.  Clouds  are  certainly  very  frequent 
upon  the  sunrise  terminator,  particularly  towards 
the  equator.  In  any  case  this  is  an  interesting  mat- 
ter for  investigation  at  future  oppositions. 

As  the  snow  in  melting  receded  towards  the  pole, 
there  was  a  narrow,  nearly  straight  region  upon 
which  it  lingered  longer  than  elsewhere.  At  present 
the  snow  is  divided  into  two  sections,  one  long  and 
narrow,  the  other  of  irregular  shape,  and  some- 
what mottled.  The  appearance  is  such  as  might  be 
produced  by  a  mountain  range  and  an  area  of  irreg- 
ular elevation,  with  a  valley  lying  between  them.  It 
was  from  this  supposed  valley  that  the  dark  line  is- 
sued in  July  connecting  it  with  the  Northern  Sea. 

Upon  August  5,  in  the  region  just  to  the  north 
of  Solis  Lacus,  latitude  —  20°,  a  small  but  con- 
spicuous white  spot  appeared.  It  was  conspicuous 
from  being  brighter  than  any  other  spot  upon  the 
planet  save  the  southern  snow  cap,  which  it  exactly 
resembled  in  color. 

A  similar  but  much  smaller  spot  was  also  noticed 
further  to  the  southwest.  Both  spots  had  disap- 
peared by  August  7,  but  careful  measurements  upon 
two  nights,  and  several  drawings,  had  already  ac- 
curately located  their  positions.  The  larger  of  these 
spots  measured  about  60  miles  in  length  by  perhaps 
40  in  width,  and  was  much  brighter  than  any  cloud 
that  I  have  ever  seen  upon  the  planet.  I  am  in- 


Mars  m  1892  61 

clined  to  attribute  both  of  these  spots  to  snow.  We 
have  frequently  seen  small  white  points  lying  along 
the  line  which  bounds  the  shaded  regions  upon  the 
north.  Early  in  August  the  whole  northern  edge 
of  the  Equatorial  Sea  was  bounded  by  a  narrow 
white  line,  while  later  a  similar  line  bounded  the 
Northern  Sea  upon  the  west.  These  lines  were  ap- 
parently due  to  cloud,  and  were  not  as  bright  as 
the  spots  of  snow  referred  to  above.  Although 
nearly  a  thousand  miles  long,  they  could  hardly  have 
exceeded  thirty  miles  in  breadth. 

Although  Mars  has  been  nearer  the  Earth  at  this 
past  opposition  than  it  will  be  again  for  fifteen  years, 
I  am  quite  inclined  to  believe  that  it  will  be  better 
seen  in  1894  than  it  has  been  this  year.  My  rea- 
sons for  this  statement  are  as  follows: — In  the  first 
place,  its  distance  from  the  Earth  will  not  be  very 
much  greater  than  it  was  this  past  year,  and  indeed 
for  part  of  the  time  it  will  be  less  remote  than  it 
was  when  many  of  our  most  interesting  observations 
were  secured.  Secondly,  it  will  be  much  farther 
north,  where  the  great  northern  telescopes  can  be 
used  upon  it  to  much  greater  advantage.  Thirdly, 
following  the  melting  of  the  southern  snow,  the 
Arean  atmosphere  was  filled  with  clouds,  and  these 
did  not  clear  away  satisfactorily  until  the  very  end 
of  August,  or  long  after  the  opposition  was  over. 
It  was  only  after  the  clouds  began  to  clear,  that  the 


6S  Mart 

Arean  lakes,  which  have  proved  such  an  interesting 
feature  of  this  opposition,  began  to  show  to  their  full 
advantage.  Owing  to  the  change  of  seasons  upon 
Mars,  little  of  this  latter  difficulty  should  be  ex- 
perienced at  the  next  opposition,  and  it  is  thought 
that  many  lakes  and  other  delicate  features  still  re- 
main undiscovered,  which  may  reveal  themselves  at 
that  time.  Could  the  great  40-inch  telescope  of 
Southern  California  then  be  completed,  undoubtedly 
the  best  views  of  the  planet  would  be  obtained  at  that 
point,  but  if  it  is  not,  the  Lick  telescope  can  cer- 
tainly be  used  to  greater  advantage,  and  the  Are- 
quipa  telescope  to  no  less  advantage,  than  was  the 
case  this  year. 


CHAPTER   VII 

i 

SCHIAPARELLFS  LATEST  VIEWS  REGARD- 
ING MARS  * 

It  is  probable  that  the  astronomer  whose  name  is 
most  closely  linked  with  the  planet  Mars  at  the 
present  time  is  Giovanni  Schiaparelli.  And  yet  al- 
though nearly  everybody  has  heard  of  Schiaparelli's 
canals,  very  few  astronomers  even,  outside  of  France 
and  Italy,  had  until  recently  more  than  a  very  vague 
notion  what  were  really  his  ideas  in  regard  to  them. 
This  is  due  probably  to  the  fact  that  he  has  written 
exclusively  in  Italian,  a  language  which  very  few 
American  astronomers,  and  I  believe  very  few  Eng- 
lish ones,  understand.  To  this  fact  chiefly  I  think  is 
due  the  great  incredulity  with  which  his  observations 
have  been  treated,  at  least  until  recently,  in  both  of 
these  countries.  Astronomers  could  understand  his 
maps,  they  knew  therefore  what  he  had  done,  but 
they  could  not  understand  his  description  of  his 
observations,  and  so  were  incredulous  regarding 
their  accuracy.  Moreover,  such  a  mass  of  detail 

1  Astronomy  and  Astro-Physics,  1894,  13,  632,  714. 
63 


64  Mart 

appeared  upon  his  maps,  which  had  not  before  been 
seen  by  others,  that  it  completely  masked  the  more 
striking  features  of  the  planet,  thus  rendering  its 
appearance  entirely  different  from  that  which  it 
presented  in  the  telescope  under  ordinary  atmospheric 
conditions. 

But  within  the  last  few  years  a  change  has  oc- 
curred. Flammarion  has  translated  a  large  part  of 
Schiaparelli's  writings  into  French,  a  language  with 
which  most  English-speaking  astronomers  are  fa- 
miliar, and  moreover  the  canals  have  been  seen  by  a 
number  of  astronomers  whose  descriptions  of  them 
in  English  and  French  could  be  understood,  and 
were  found  to  agree  with  those  of  Schiaparelli. 

But  errors  are  still  frequently  made  by  people 
who  might  be  expected  to  know  better.  Thus,  many 
people  suppose  that  Schiaparelli  was  the  original 
discoverer  of  canals,  a  claim  which  he  never  made 
for  himself.  In  point  of  fact  some  of  them  appear 
upon  maps  of  the  planet  published  more  than  fifty 
years  ago.  The  former  English  incredulity  in  the 
matter  seems  the  more  strange,  since  many  of  the 
canals  were  seen  by  Dawes  in  1864,  and  by  Burton 
and  Dreyer  in  1879.  Schiaparelli  however  has  dis- 
covered far  more  canals  than  anyone  else,  and  he  is 
also  the  discoverer  of  their  gemination. 

In  this  connection  it  may  be  that  a  brief  chrono- 
logical statement  of  the  more  important  facts  and 


Schiaparelli's  Latest  Views  Regarding  Mart     65 

discoveries  relating  to  Mars  will  not  be  without 
interest.  In  compiling  it  I  have  been  chiefly  indebted 
to  Flammarion's  classic  work  "La  Planete  Mars," 
although  other  sources  have  also  been  consulted. 

272  B.  c.  The  first  known  observation  of  Mars  is 
recorded  in  Ptolemy's  Almagest. 

1610.  The  phases  of  Mars  were  discovered  by 
Galileo. 

1659.  The  first  sketch  showing  surface  detail  was 
made  by  Huyghens.  He  also  suggested  a  rotation 
in  24  hours. 

1666.  Cassini  determined  the  rotation  of  Mars 
to  take  place  in  24  hours  40  minutes.  He  also  ob- 
served the  polar  caps,  and  "he  distinguished  on 
the  disc  of  Mars,  near  the  terminator,  a  white  spot 
advancing  into  the  dark  portion  and  representing 
without  doubt,  like  those  of  the  Moon,  a  roughness 
or  irregularity  of  surface."  This  latter  statement 
is  curious,  but  the  effect  was  undoubtedly  due  to 
irradiation,  since  his  telescope  was  entirely  inad- 
equate to  enable  him  to  observe  such  a  delicate 
phenomenon. 

1777.  With  the  exception  of  Huyghens,  Hooke, 
and  possibly  Maraldi,  no  one  succeeded  in  making 
recognizable  sketches  of  the  surface  detail  upon 
Mars  for  over  a  century,  until  Sir  William  Herschel 
took  the  matter  up  this  year. 

1783.    Sir  William  Herschel  detected  the  varia- 


66  Mars 

tion  of  the  size  of  the  polar  snow  caps  with  the 
seasons,  measured  the  polar  compression,  and  deter- 
mined the  inclination  of  the  axis  of  the  planet  to 
its  orbit. 

1785-1802.  Schroeter  made  an  extended  study  of 
the  planet.  His  drawings  are  upon  the  whole  rather 
better  than  those  of  Herschel.  He  discovered  among 
other  things  the  very  dark  spots  to  which  I  have 
referred  in  my  publications  as  the  Northern  and 
Equatorial  Seas.  He,  however,  supposed  them  to  be 
clouds. 

1840.  Beer  and  Maedler  published  the  first  map 
of  the  planet  assigning  latitudes  and  longitudes  to 
the  various  markings.  On  this  map  are  indicated  the 
first  canals,  and  the  first  of  the  small  lakes,  so  many 
of  which  have  been  discovered  during  the  last  few 
years.  The  canals  are  Nectar  and  Agathodaemon 
and  portions  of  Hades  and  Tartarus.  The  lake  is 
Lacus  Phoenicis.  Their  map  is  the  first  satisfactory 
representation  of  the  entire  surface  of  the  planet. 
The  only  region  which  previous  observers  had 
clearly  distinguished  was  that  in  the  vicinity  of  the 
Syrtis  Major. 

1858.  Secchi  made  a  careful  study  of  the  colors 
exhibited  by  the  planet. 

1862.  Lockyer  made  the  first  series  of  really 
good  sektches  of  the  planet,  showing  all  the  charac- 
teristic forms  with  which  we  are  now  so  familiar. 


Sckiaparelli's  Latest  Views  Regarding  Mars      67 

His  drawings,  and  also  those  of  some  of  the  other 
observers,  give  the  first  indications  of  the  appear- 
ance of  the  central  branch  in  the  Y,  so  called  by 
Secchi. 

1864.  Dawes  detected  eight  or  ten  of  the  canals. 

1867.  Huggins  detected  lines  due  to  the  presence 
of  water  vapor  in  the  spectrum  of  Mars. 

1867.  Proctor  determined  the  period  of  rotation 
of  Mars  within  0.1  second. 

1877.  Hall  discovered  the  two  satellites  of  Mars. 

1877.  Green  made  a  very  excellent  series  of 
drawings  of  the  planet,  superior  to  anything  which 
had  preceded  them. 

1877.  Schiaparelli  made  the  first  extensive  tri- 
angulation  of  the  surface  of  the  planet,  and  added 
very  largely  to  the  number  of  known  canals. 

1879.  Schiaparelli  detected  the  gemmation  of 
Nilus, — the  first  known  double  canal. 

1882.  Schiaparelli  discovered  numerous  double 
canals,  and  announced  that  the  appearance  formed 
one  of  the  characteristic  phenomena  of  the  planet. 

The  most  reliable  confirmation  of  this  phenomenon 
hitherto  reported  has  come  from  Perrotin  of  Nice, 
and  A.  Stanley  Williams  in  England.  If  Schiapa- 
relli's  theory  is  correct,  that  the  duplication  occurs 
only  between  the  spring  and  autumn  equinoxes  of 
the  northern  hemisphere,  the  last  opportunity  to 
witness  it  was  in  1890,  and  the  next  in  January  and 


68  Mart 

February  of  1895,  unless  the  planet  proves  to  be 
too  remote  at  that  period. 

Very  few  of  Schiaparelli's  writings  have  ever  been 
translated  into  English,  and  none  so  far  as  I  know, 
hitherto,  without  the  intervention  of  some  other 
language,  such  as  German  or  French.  The  following 
translation  is  from  "Natura  ed  Arte"  for  February 
15,  1893.  It  gives  the  latest  expression  of  his  views 
upon  the  periodical  inundations  experienced  by  the 
planet,  upon  the  nature  of  the  seas,  the  canals,  and 
the  gemination  of  the  latter. 

THE  PLANET  MARS 

GIOVANNI    SCHIAPABEI/LI 

Many  of  the  first  astronomers  who  studied  Mars 
with  the  telescope,  had  noted  on  the  outline  of  its 
disc  two  brilliant  white  spots  of  rounded  form  and 
of  variable  size.  In  process  of  time  it  was  observed 
that  whilst  the  ordinary  spots  upon  Mars  were  dis- 
placed rapidly  in  consequence  of  its  daily  rotation, 
changing  in  a  few  hours  both  their  position  and 
their  perspective,  that  the  two  white  spots  remained 
sensibly  motionless  at  their  posts.  It  was  concluded 
rightly  from  this,  that  they  must  occupy  the  poles 
of  rotation  of  the  planet,  or  at  least  must  be  found 
very  near  to  them.  Consequently  they  were  given 
the  name  of  polar  caps  or  spots.  And  not  without 


Schiaparelli's  Latest  Views  Regarding  Mars     69 

reason  is  it  conjectured,  that  these  represent  upon 
Mars  that  immense  mass  of  snow  and  ice,  which 
still  today  prevents  navigators  from  reaching  the 
poles  of  the  Earth.  We  are  led  to  this  conclusion 
not  only  by  the  analogy  of  aspect  and  of  place,  but 
also  by  another  important  observation. 


As  things  stand,  it  is  manifest,  that  if  the  above 
mentioned  white  polar  spots  of  Mars  represent  snow 
and  ice,  they  should  continue  to  decrease  in  size 
with  the  approach  of  summer  in  those  places,  and 
increase  during  the  winter.  Now  this  very  fact  is 
observed  in  the  most  evident  manner.  In  the  second 
half  of  the  year  1892  the  southern  polar  cap  was 
in  full  view;  during  that  interval,  and  especially  in 
the  months  of  July  and  August,  its  rapid  diminu- 
tion from  week  to  week  was  very  evident,  even  to 
those  observing  with  common  telescopes.  This  snow, 
(for  we  may  well  call  it  so,)  which  in  the  beginning 
reached  as  far  as  latitude  70°,  and  formed  a  cap 
of  over  2,000  kilometers  (1,200  miles)  in  diameter, 
progressively  diminished,  so  that  two  or  three  months 
later  little  more  of  it  remained  than  an  area  of 
perhaps  300  kilometers,  (180  miles)  at  the  most, 
and  still  less  was  seen  later  in  the  last  days  of  1892. 
In  these  months  the  southern  hemisphere  of  Mars 
had  its  summer;  the  summer  solstice  occurring  upon 


70  Mars 

October  13.  Correspondingly  the  mass  of  snow 
surrounding  the  northern  pole  should  have  increased ; 
but  this  fact  was  not  observable,  since  that  pole 
was  situated  in  the  hemisphere  of  Mars  which  was 
opposite  to  that  facing  the  Earth.  The  melting  of 
the  northern  snow  was  seen  in  its  turn  in  the  years 
1882,  1884  and  1886. 

These  observations  of  the  alternate  increase  and 
decrease  of  the  polar  snows  are  easily  made,  even 
with  telescopes  of  moderate  power,  but  they  become 
much  more  interesting  and  instructive  when  we  can 
follow  assiduously  the  changes  in  their  more  minute 
particulars,  using  larger  instruments.  The  snowy 
regions  are  then  seen  to  be  successively  notched  at 
their  edges ;  black  holes  and  huge  fissures  are  formed 
in  their  interiors;  great  isolated  pieces  many  miles 
in  extent  stand  out  from  the  principal  mass,  and 
dissolving  disappear  a  little  later.  In  short,  the 
same  divisions  and  movements  of  these  icy  fields 
present  themselves  to  us,  at  a  glance,  that  occur 
during  the  summer  of  our  own  arctic  regions,  ac- 
cording to  the  descriptions  of  explorers. 

The  southern  snow,  however,  presents  this  pecu- 
liarity, that  the  center  of  its  irregularly  rounded 
figure  does  not  coincide  exactly  with  the  pole,  but 
is  situated  at  another  point,  which  is  nearly  always 
the  same,  and  is  distant  from  the  pole  about  300 
kilometers  (180  miles)  in  the  direction  of  the  Mare 


Schiaparelli's  Latest  Views  Regarding  Mars     71 

Erythraeum.  From  this  we  conclude  that  when  the 
area  of  the  snow  is  reduced  to  its  smallest  extent, 
that  the  south  pole  of  Mars  is  uncovered;  and 
therefore  perhaps,  the  problem  of  reaching  it  upon 
this  planet  is  easier  than  upon  the  Earth.  The 
southern  snow  is  in  the  midst  of  a  huge  dark  spot, 
which  with  its  branches  occupies  nearly  one-third 
of  the  whole  surface  of  Mars,  and  is  supposed  to 
represent  its  principal  ocean.  Hence  the  analogy 
with  our  arctic  and  antarctic  snows  may  be  said  to 
be  complete,  and  especially  so  with  the  antarctic  one. 
The  mass  of  the  northern  snow-cap  of  Mars  is  on 
the  other  hand  centered  almost  exactly  upon  its 
pole.  It  is  located  in  a  region  of  yellow  color,  which 
we  are  accustomed  to  consider  as  representing  the 
continent  of  the  planet.  From  this  arises  a  singular 
phenomenon  which  has  no  analogy  upon  the  Earth. 
At  the  melting  of  the  snows,  accumulated  at  that 
pole  during  the  long  night  of  ten  months  and  more, 
the  liquid  mass  produced  in  that  operation  is  dif- 
fused around  the  circumference  of  the  snowy  region, 
converting  a  large  zone  of  surrounding  land  into  a 
temporary  sea,  and  filling  all  the  lower  regions. 
This  produces  a  gigantic  inundation,  which  has  led 
some  observers  to  suppose  the  existence  of  another 
ocean  in  those  parts,  but  which  does  not  really  exist 
in  that  place,  at  least  as  a  permanent  sea.  We  see 
then,  (the  last  opportunity  was  in  1884),  the  white 


7*  Mars 

spot  of  the  snow  surrounded  by  a  dark  zone,  which 
follows  its  perimeter  in  its  progressive  diminution, 
upon  a  circumference  ever  more  and  more  narrow. 
The  outer  part  of  this  zone  branches  out  into  dark 
lines  which  occupy  all  the  surrounding  region,  and 
seem  to  be  distributary  canals,  by  which  the  liquid 
mass  may  return  to  its  natural  position.  This  pro- 
duces in  these  regions  very  extensive  lakes,  such  as 
that  designated  upon  the  map  by  the  name  of  Lacus 
Hyperboreus;  the  neighboring  interior  sea  called 
Mare  Acidalium  becomes  more  black,  and  more  con- 
spicuous. And  it  is  to  be  remembered  as  a  very 
probable  thing,  that  the  flowing  of  this  melted 
snow  is  the  cause  which  determines  principally  the 
hydrographic  state  of  the  planet,  and  the  variations 
that  are  periodically  observed  in  its  aspect.  Some- 
thing similar  would  be  seen  upon  the  Earth,  if  one 
of  our  poles  came  to  be  located  suddenly  in  the  cen- 
ter of  Asia  or  Africa.  As  things  stand  at  present, 
we  may  find  a  miniature  image  of  these  conditions  in 
the  flooding  that  is  observed  in  our  streams  at  the 
melting  of  the  Alpine  snows. 

Travellers  in  the  arctic  regions  have  frequent 
occasion  to  observe  how  the  state  of  the  polar  ice 
at  the  beginning  of  the  summer,  and  even  at  the 
beginning  of  July  is  always  very  unfavorable  to 
their  progress.  The  best  season  for  exploration  is 
in  the  month  of  August,  and  September  is  the  month 


Schiaparelli's  Latest  Views  Regarding  Mars      73 

in  which  the  trouble  from  the  ice  is  the  least.  Thus 
in  September  our  Alps  are  usually  more  practicable 
than  at  any  other  season.  And  the  reason  for  it  is 
clear,  the  melting  of  the  snow  requires  time,  a  high 
temperature  is  not  sufficient,  it  is  necessary  that  it 
should  continue,  and  its  effect  will  be  so  much  the 
greater,  as  it  is  the  more  prolonged.  Thus,  if  we 
could  slow  down  the  course  of  our  seasons,  so  that 
each  month  should  last  sixty  days  instead  of  thirty, 
in  the  summer  in  such  a  lengthened  condition,  the 
melting  of  the  ice  would  progress  much  further,  and 
perhaps  it  would  not  be  an  exaggeration  to  say  that 
the  polar  cap  at  the  end  of  the  warm  season  would 
be  entirely  destroyed.  But  one  cannot  doubt  in  any 
case,  that  the  fixed  portion  of  such  a  cap  would 
be  reduced  to  much  smaller  size  than  we  see  it  today. 
Now  this  is  exactly  what  happens  in  Mars.  The 
long  year,  nearly  double  our  own,  permits  the  ice 
to  accumulate  during  the  polar  night  of  ten  or  twelve 
months,  so  as  to  descend  in  the  form  of  a  continuous 
layer  as  far  as  parallel  70°,  or  even  further.  But 
in  the  day  which  follows  of  twelve  months  or  ten 
months,  the  Sun  has  time  to  melt  all  or  nearly  all, 
of  the  snow  of  recent  formation,  reducing  it  to  such 
a  small  area,  that  it  seems  to  us  no  more  than  a 
very  white  point.  And  perhaps  this  snow  is  entirely 
destroyed,  but  of  this  there  is  at  present  no  satis- 
factory observation* 


74  Mars 

Other  white  spots  of  a  transitory  character,  and 
of  a  less  regular  arrangement  are  formed  in  the 
southern  hemisphere,  upon  the  islands  near  the  pole, 
and  also  in  the  opposite  hemisphere,  whitish  regions 
appear  at  times  surrounding  the  north  pole,  and 
reaching  to  50°  and  55°  of  latitude.  They  are  per- 
haps transitory  snows,  similar  to  those  which  are 
observed  in  our  latitudes.  But  also  in  the  torrid 
zone  of  Mars  are  seen  some  very  small  white  spots 
more  or  less  persistent,  amongst  others  one  was  seen 
by  me  in  three  consecutive  oppositions  (1877-1882) 
at  the  point  indicated  upon  our  chart  by  longitude 
268°  and  latitude  16°  north.  Perhaps  we  may  be 
permitted  to  imagine  in  this  place  the  existence  of 
a  mountain  capable  of  supporting  extensive  ice- 
fields. The  existence  of  such  a  mountain  has  been 
supposed  also  by  some  recent  observers,  founded 
upon  other  facts. 

As  has  been  stated,  the  polar  snows  of  Mars  prove 
in  an  incontrovertible  manner,  that  this  planet,  like 
the  Earth,  is  surrounded  by  an  atmosphere  capable 
of  transporting  vapor  from  one  place  to  another. 
These  snows  are  in  fact  precipitations  of  vapor, 
condensed  by  the  cold,  and  carried  with  it  succes- 
sively. How  carried  with  it,  if  not  by  atmospheric 
movement?  The  existence  of  an  atmosphere  charged 
with  vapor  has  been  confirmed  also  by  spectroscopic 
observations,  principally  those  of  Vogel;  according 


Schiaparelli's  Latest  Views  Regarding  Mars     75 

to  which  this  atmosphere  must  be  of  a  composition 
differing  little  from  our  own,  and  above  all  very 
rich  in  aqueous  vapor.  This  is  a  fact  of  the  highest 
importance,  because  from  it  we  can  rightly  affirm 
with  much  probability,  that  to  water,  and  to  no 
other  liquid  is  due  the  seas  of  Mars  and  its  polar 
snows.  When  this  conclusion  is  assured  beyond  all 
doubt,  another  one  may  be  derived  from  it,  of  not 
less  importance, — that  the  temperature  of  the  Arean 
climate,  notwithstanding  the  greater  distance  of  that 
planet  from  the  Sun,  is  of  the  same  order  as  the 
temperature  of  the  terrestrial  one.  Because,  if  it 
were  true,  as  has  been  supposed  by  some  investi- 
gators, that  the  temperature  of  Mars  was  on  the 
average  very  low  (from  50°  to  60°  below  zero)  it 
would  not  be  possible  for  water  vapor  to  be  an  im- 
portant element  in  the  atmosphere  of  that  planet, 
nor  could  water  be  an  important  facftor  in  its 
physical  changes;  but  would  give  place  to  carbonic 
acid,  or  to  some  other  liquid  whose  freezing  point 
was  much  lower. 

The  elements  of  the  meteorology  of  Mars  seem 
then  to  have  a  close  analogy  to  those  of  the  Earth. 
But  there  are  not  lacking,  as  might  be  expected, 
causes  of  dissimilarity.  From  circumstances  of  the 
smallest  moment,  nature  brings  forth  an  infinite 
variety  in  its  operations.  Of  the  greatest  influence 
must  be  the  different  arrangement  of  the  seas  and 


76  Mars 

the  continents  upon  Mars,  and  upon  the  Earth, 
regarding  which,  a  glance  at  the  map  will  say  more 
than  would  be  possible  in  many  words.  We  have 
already  emphasized  the  fact  of  the  extraordinary 
periodical  flood,  which  at  every  revolution  of  Mars 
inundates  the  northern  polar  region  at  the  melting 
of  the  snow.  Let  us  now  add  that  this  inundation  is 
spread  out  to  a  great  distance  by  means  of  a  net- 
work of  canals,  perhaps  constituting  the  principal 
mechanism  (if  not  the  only  one)  by  which  water 
(and  with  it  organic  life)  may  be  diffused  over  the 
arid  surface  of  the  planet.  Because  on  Mars  it  rains 
very  rarely,  or  perhaps  even,  it  does  not  rain  at 
all.  And  this  is  the  proof. 

Let  us  carry  ourselves  in  imagination  into  celes- 
tial space,  to  a  point  so  distant  from  the  Earth,  that 
we  may  embrace  it  all  at  a  single  glance.  He  would 
be  greatly  in  error  who  had  expected  to  see  repro- 
duced there,  upon  a  great  scale,  the  image  of  our 
continents,  with  their  gulfs  and  islands,  and  with  the 
seas  that  surround  them,  which  are  seen  upon  our 
artificial  globes.  There  without  doubt  the  known 
forms,  or  part  of  them,  would  be  seen  to  appear 
under  a  vaporous  veil,  but  a  great  part  (perhaps 
one-half)  of  the  surface  would  be  rendered  invisible 
by  the  immense  fields  of  cloud,  continually  varying 
in  density,  in  form  and  in  extent.  Such  a  hindrance, 
most  frequent  and  continuous  in  the  polar  regions, 


Schiaparelli's  Latest  Views  Regarding  Mars      77 

would  still  impede  nearly  half  the  time  the  view  of 
the  temperate  zones,  distributing  itself  in  capricious 
and  ever  varying  configurations.  The  seas  of  the 
torrid  zone  would  be  seen  to  be  arranged  in  long 
parallel  layers,  corresponding  to  the  zone  of  equa- 
torial and  tropical  calms.  For  an  observer  placed 
upon  the  Moon,  the  study  of  our  geography  would 
not  be  so  simple  an  undertaking  as  one  might  at  first 
imagine. 

There  is  nothing  of  this  sort  in  Mars.  In  every 
climate,  and  under  every  zone,  its  atmosphere  is 
nearly  perpetually  clear,  and  sufficiently  transparent 
to  permit  one  to  recognize  at  any  moment  whatever, 
the  contours  of  the  seas  and  continents,  and  more 
than  that,  even  the  minor  configurations.  Not  in- 
deed that  vapors  of  a  certain  degree  of  opacity  are 
lacking,  but  they  offer  very  little  impediment  to 
the  study  of  the  topography  of  the  planet.  Here 
and  there  we  see  appear  from  time  to  time  a  few 
whitish  spots  changing  their  position  and  form, 
rarely  extending  over  a  very  wide  area.  They  fre- 
quent by  preference  a  few  regions,  such  as  the  islands 
of  the  Mare  Australe,  and  on  the  continents,  the 
regions  designated  on  the  map  with  the  names  of 
Elysium  and  Tempe.  Their  brilliancy  generally  di- 
minishes and  disappears  at  the  meridian  hour  of  the 
place,  and  is  reinforced  in  the  morning  and  even- 
ing, with  very  marked  variations.  It  is  possible  that 


78  Mars 

they  may  be  layers  of  cloud,  because  the  upper  por- 
tions of  terrestrial  clouds,  where  they  are  illuminated 
by  the  Sun,  appear  white.  But  various  observa- 
tions lead  us  to  think  that  we  are  dealing  rather  with 
a  thin  veil  of  fog,  instead  of  a  true  nimbus  cloud, 
carrying  storms  and  rain.  Indeed  it  may  be  merely 
a  temporary  condensation  of  vapor,  under  the  form 
of  dew  or  hoar  frost. 

Accordingly,  as  far  as  we  may  be  permitted  to 
argue  from  the  observed  facts,  the  climate  of  Mars 
must  resemble  that  of  a  clear  day  upon  a  high  moun- 
tain. By  day  a  very  strong  solar  radiation  hardly 
mitigated  at  all  by  mist  or  vapor,  by  night  a  copious 
radiation  from  the  soil  towards  celestial  space,  and 
because  of  that  a  very  marked  refrigeration.  Hence 
a  climate  of  extremes,  and  great  changes  of  temper- 
ature from  day  to  night,  and  from  one  season  to 
another.  And  as  on  the  Earth  at  altitudes  of  5,000 
and  6,000  meters  (17,000  to  20,000  feet),  the  vapor 
of  the  atmosphere  is  condensed  only  into  the  solid 
form,  producing  those  whitish  masses  of  suspended 
crystals,  which  we  call  cirrus  clouds,  so  in  the  at- 
mosphere of  Mars,  it  would  be  rarely  possible  (or 
would  even  be  impossible)  to  find  collections  of  cloud 
capable  of  producing  rain  of  any  consequence.  The 
variation  of  the  temperature  from  one  season  to  an- 
other would  be  notably  increased  by  their  long  dura- 
tion, and  thus  we  can  understand  the  great  freezing 


SchiapareUi's  Latest  Views  Regarding  Mars      79 

and  melting  of  the  snow,  which  is  renewed  in  turn  at 
the  poles  at  each  complete  revolution  of  the  planet 
around  the  Sun. 

As  our  chart  demonstrates,  in  its  general  topog- 
raphy Mars  does  not  present  any  analogy  with  the 
Earth.  A  third  of  the  surface  is  occupied  by  the 
great  Mare  Australe,  which  is  strewn  with  many  is- 
lands, and  the  continents  are  cut  up  by  gulfs  and 
ramifications  of  various  forms.  To  the  general  wa- 
ter system  belongs  an  entire  series  of  small  internal 
seas,  of  which  the  Hadriacum  and  the  Tyrrhenum 
communicate  with  it  by  wide  mouths,  whilst  the  Cim- 
merium,  the  Sirenum  and  the  Solis  Lacus  are  con- 
nected with  it  only  by  means  of  narrow  canals.  We 
shall  notice  in  the  first  four  a  parallel  arrangement, 
which  certainly  is  not  accidental,  as  also  not  with- 
out reason  is  the  corresponding  position  of  the  pe- 
ninsulas of  Ausonia,  Hesperia  and  Atlantis.  The 
color  of  the  seas  of  Mars  is  generally  brown,  mixed 
with  grey,  but  not  always  of  equal  intensity  in  all 
places,  nor  is  it  the  same  in  the  same  place  at  all 
times.  From  an  absolute  black  it  may  descend  to 
a  light  gray,  or  to  an  ash  color.  Such  a  diversity 
of  colors  may  have  its  origin  in  various  causes,  and 
is  not  without  analogy  also  upon  the  Earth,  where 
it  is  noted  that  the  seas  of  the  warm  zone  are  usually 
much  darker  than  those  nearer  the  pole.  The  water 
of  the  Baltic,  for  example,  has  a  light,  muddy  color, 


80  Mart 

that  is  not  observed  in  the  Mediterranean.  And  thus 
in  the  seas  of  Mars,  we  see  the  color  become  darker 
when  the  Sun  approaches  their  zenith,  and  summer 
begins  to  rule  in  that  region. 

All  of  the  remainder  of  the  planet,  as  far  as  the 
north  pole,  is  occupied  by  the  mass  of  the  conti- 
nents, in  which,  save  in  a  few  areas  of  relatively 
small  extent,  an  orange  color  predominates,  which 
sometimes  reaches  a  dark  red  tint,  and  in  others  de- 
scends to  yellow  and  white.  The  variety  in  this 
coloring  is  in  part  of  meteorological  origin,  in  part 
it  may  depend  on  the  diverse  nature  of  the  soil,  but 
upon  its  real  cause  it  is  not  as  yet  possible  to  frame 
any  very  well  grounded  hypothesis.  Nevertheless, 
the  cause  of  this  predominance  of  the  red  and  yellow 
tints  upon  the  surface  of  ancient  Pyrois  is  well 
known.2  Some  have  thought  to  attribute  this  color- 
ing to  the  atmosphere  of  Mars,  through  which  the 
surface  of  the  planet  might  be  seen  colored,  as  any 
terrestrial  object  becomes  red,  when  seen  through 
red  glass.  But  many  facts  are  opposed  to  this  idea, 
among  others,  that  the  polar  snows  appear  always 
of  the  purest  white,  although  the  rays  of  light  de- 
rived from  them  traverse  twice  the  atmosphere  of 
Mars  under  great  obliquity.  We  must  then  con- 

9  Pyrois  I  take  to  be  some  terrestrial  region,  although  I  have 
not  been  able  to  find  any  translation  of  the  name. — Tr. 


Schiaparelli's  Latest  Views  Regarding  Mars     81 

elude  that  the  Arean  continents  appear  red  and  yel- 
low, because  they  are  so  in  fact. 

Besides  these  dark  and  light  regions,  which  we 
have  described  as  seas  and  continents,  and  of  whose 
nature  there  is  at  present  scarcely  left  any  room 
for  doubt,  some  others  exist,  truly  of  small  extent, 
of  an  amphibious  nature,  which  sometimes  appear 
yellowish  like  the  continents,  and  are  sometimes 
clothed  in  brown  (even  black  in  certain  cases)  and 
assume  the  appearance  of  seas,  whilst  in  other  cases 
their  color  is  intermediate  in  tint,  and  leaves  us  in 
doubt  to  which  class  of  regions  they  may  belong. 
Thus  all  the  islands  scattered  through  the  Mare 
Australe  and  the  Mare  Erythraeum  belong  to  this 
category,  so  too  the  long  peninsulas  called  Deuca- 
lionis  Regio  and  Pyrrhae  Regio,  and  in  the  vicinity 
of  the  Mare  Acidalium  the  regions  designated  by  the 
names  of  Baltia  and  Nerigos.  The  most  natural  idea, 
and  the  one  to  which  we  should  be  led  by  analogy,  is 
to  suppose  these  regions  to  represent  huge  swamps,  in 
which  the  variation  in  depth  of  the  water  produces 
the  diversity  of  colors.  Yellow  would  predominate 
in  those  parts  where  the  depth  of  the  liquid  layer 
was  reduced  to  little  or  nothing,  and  brown,  more  or 
less  dark,  in  these  places  where  the  water  was  suffi- 
ciently deep  to  abosrb  more  light,  and  to  render  the 
bottom  more  or  less  invisible.  That  the  water  of  the 
sea,  or  any  other  deep  and  transparent  water,  seen 


82  Mars 

from  above,  appears  more  dark  the  greater  the  depth 
of  the  liquid  stratum,  and  that  the  land  in  compari- 
son with  it  appears  bright  under  the  solar  illumi- 
nation, is  known  and  confirmed  by  certain  physical 
reasons.  The  traveller  in  the  Alps  often  has  occa- 
sion to  convince  himself  of  it,  seeing  from  the  sum- 
mits, the  deep  lakes  with  which  the  region  is  strewn, 
extending  under  his  feet  as  black  as  ink,  whilst  in 
contrast  with  them  even  the  blackest  rocks  illumined 
by  the  sunlight  appear  brilliant.3 

Not  without  reason  then  have  we  hitherto  attrib- 
uted to  the  dark  spots  of  Mars  the  part  of  seas,  and 
that  of  continents  to  the  reddish  areas  which  occupy 
nearly  two-thirds  of  all  the  planet,  and  we  shall  find 
later,  other  reasons  which  confirm  this  method  of 
reasoning.  The  continents  form  in  the  northern 
hemisphere  a  nearly  continuous  mass,  the  only  im- 
portant exception  being  the  great  lake  called  the 
Mare  Acidalium,  of  which  the  extent  may  vary  ac- 
cording to  the  time,  and  which  is  connected  in  some 
way  with  the  inundations  which  we  have  said  were 
produced  by  the  melting  of  the  snow  surrounding  the 
north  pole. 

To  the  system  of  the  Mare  Acidalium  undoubt- 

•This  observation  of  the  dark  color  which  deep  water  ex- 
hibits when  seen  from  above,  is  found  already  noted  by  the 
first  author  of  antique  memory,  for  in  the  Iliad  (verses  770-1 
of  book  V)  it  is  described  how  "the  sentinel  from  the  high 
sentry-box  extends  his  glance  over  the  wine-colored  sea."  In 
the  version  of  Monti  the  adjective  indicating  the  color  is  lost. 


Schiaparelli'g  Latest  Views  Regarding  Mart     88 

edly  belong  the  temporary  lakes  called  Lacus  Hyper- 
boreus  and  the  Lacus  Niliacus.  This  last  is  ordi- 
narily separated  from  the  Mare  Acidalium  by  means 
of  an  isthmus  or  regular  dam,  of  which  the  continu- 
ity was  only  seen  to  be  broken  once  for  a  short  time 
in  1888.  Other  smaller  dark  spots  are  found  here 
and  there  in  the  continental  area,  which  we  may 
designate  as  lakes,  but  they  are  certainly  not  perma- 
nent lakes  like  ours,  but  are  variable  in  appearance 
and  size  according  to  the  seasons,  to  the  point  of 
wholly  disappearing  under  certain  circumstances. 
Ismenius  Lacus,  Lunae  Lacus,  Trivium  Charontis 
and  Propontis  are  the  most  conspicuous  and  durable 
ones.  There  are  also  smaller  ones,  such  as  Lacus 
Moeris  and  Fons  Juventae  which  at  their  maximum 
size  do  not  exceed  100  to  150  kilometers  (60  to  90 
miles)  in  diameter,  and  are  among  the  most  difficult 
objects  upon  the  planet. 

All  the  vast  extent  of  the  continents  is  furrowed 
upon  every  side  by  a  network  of  numerous  lines  or 
fine  stripes  of  a  more  or  less  pronounced  dark  color 
whose  aspect  is  very  variable.  These  traverse  the 
planet  for  long  distances  in  regular  lines,  that  do 
not  at  all  resemble  the  winding  courses  of  our 
streams.  Some  of  the  shorter  ones  do  not  reach  500 
kilometers  (300  miles),  others  on  the  other  hand  ex- 
tend for  many  thousands,  occupying  a  quarter  or 
sometimes  even  a  third  of  a  circumference  of  the 


84  Mart 

planet.  Some  of  these  are  very  easy  to  see,  espe- 
cially that  one  which  is  near  the  extreme  left-hand 
limit  of  our  map,  and  is  designated  by  the  name  of 
Nilosyrtis.  Others  in  turn  are  extremely  difficult, 
and  resemble  the  finest  thread  of  spider's  web  drawn 
across  the  disc.  They  are  subject  also  to  great 
variations  in  their  breadth,  which  may  reach  200  or 
even  300  kilometers  (120  to  180  miles)  for  the 
Nilosyrtis,  whilst  some  are  scarcely  30  kilometers 
(18  miles)  broad. 

These  lines  or  stripes  are  the  famous  canals  of 
Mars,  of  which  so  much  has  been  said.  As  far  as 
we  have  been  able  to  observe  them  hitherto,  they  are 
certainly  fixed  configurations  upon  the  planet.  The 
Nilosyrtis  has  been  seen  in  that  place  for  nearly  one 
hundred  years,  and  some  of  the  others  for  at  least 
thirty  years.  Their  length  and  arrangement  are 
constant,  or  vary  only  between  very  narrow  limits. 
Each  of  them  always  begins  and  ends  between  the 
same  regions.  But  their  appearance  and  their  de- 
gree of  visibility  vary  greatly,  for  all  of  them,  from 
one  opposition  to  another,  and  even  from  one  week 
another,  and  these  variations  do  not  take  place 
simultaneously  and  according  to  the  same  laws  for 
all,  but  in  most  cases  happen  apparently  capricious- 
ly, or  at  least  according  to  laws  not  sufficiently 
simple  for  us  to  be  able  to  unravel.  Often  one  or 
more  become  indistinct,  or  even  wholly  invisible, 


SMaparelWs  Latest  Views  Regardmg  Mars     85 

whilst  others  in  their  vicinity  increase  to  the  point 
of  becoming  conspicuous  even  in  telescopes  of  mod- 
erate power.  The  first  of  our  maps  shows  all  those 
that  have  been  seen  in  a  long  series  of  observations. 
This  does  not  at  all  correspond  to  the  appearance  of 
Mars  at  any  given  period,  because  generally  only  a 
few  are  visible  at  once.4 

Every  canal  (for  now  we  shall  so  call  them)  opens 
at  its  end  either  into  a  sea,  or  into  a  lake,  or  into 
another  canal,  or  else  into  the  intersection  of  several 
other  canals.  None  of  them  have  yet  been  seen  cut 
off  in  the  middle  of  the  continent,  remaining  with- 
out beginning  or  without  end.  This  fact  is  of  the 
highest  importance. 

The  canals  may  intersect  among  themselves  at  all 
possible  angles,  but  by  preference  they  converge  to- 

4  In  a  footnote  the  author  refers  to  a  drawing  of  Mars  made 
by  himself,  September  15,  1892,  and  says  "...  At  the  top  of 
the  disc  the  Mare  Erythraeum  and  the  Mare  Australe  appear 
divided  by  a  great  curved  peninsula,  shaped  like  a  sickle,  pro- 
ducing an  unusual  appearance  in  the  area  called  Deucalionis 
Regio,  which  was  prolonged  that  year  so  as  to  reach  the  islands 
of  Noachis  and  Argyre.  This  region  forms  with  them  a  con- 
tinuous whole,  but  with  faint  traces  of  separation  occurring 
here  and  there  in  a  length  of  nearly  6,000  kilometers  (4,000 
miles).  Its  color,  much  less  brilliant  than  that  of  the  con- 
tinents, was  a  mixture  of  their  yellow  with  the  brownish  grey 
of  the  neighboring  seas."  The  interesting  feature  of  this  note 
is  the  remark  that  it  was  an  unusual  appearance,  the  region 
referred  to  being  that  in  which  the  central  branch  of  the  fork 
of  the  Y  appeared.  Since  no  such  branch  was  conspicuously 
visible  this  year,  it  would  therefore  seem,  from  the  above, 
that  it  was  the  opposition  of  1892  that  was  peculiar,  and  not 
the  present  one. — Tr. 


86  Mars 

wards  the  small  spots  to  which  we  have  given  the 
name  of  lakes.  For  example,  seven  are  seen  to  con- 
verge in  Lacus  Phoenicis,  eight  in  Trivium  Charontis, 
six  in  Lunae  Lacus  and  six  in  Ismenius  Lacus. 

The  normal  appearance  of  a  canal  is  that  of  a 
nearly  uniform  stripe,  black,  or  at  least  of  a  dark 
color,  similar  to  that  of  the  seas,  in  which  the  regu- 
larity of  its  general  course  does  not  exclude  small 
variations  in  its  breadth,  and  small  sinuosities  in  its 
two  sides.  Often  it  happens  that  such  a  dark  line 
opening  out  upon  the  sea  is  enlarged  into  the  form  of 
a  trumpet,  forming  a  huge  bay,  similar  to  the  estu- 
aries of  certain  terrestrial  streams.  The  Margariti- 
fer  Sinus,  the  Aonius  Sinus,  the  Aurorae  Sinus,  and 
the  two  horns  of  the  Sabaeus  Sinus  are  thus  formed, 
at  the  mouths  of  one  or  more  canals,  opening  into 
the  Mare  Erythraeum  or  into  the  Mare  Australe. 
The  largest  example  of  such  a  gulf  is  the  Syrtis 
Major,  formed  by  the  vast  mouth  of  the  Nilosyrtis, 
so  called.  This  gulf  is  not  less  than  1,800  kilometers 
(1,100  miles)  in  breadth,  and  attains  nearly  the 
same  extent  in  a  longitudinal  direction.  Its  surface 
is  little  less  than  that  of  the  Bay  of  Bengal.  In  this 
case  we  see  clearly  the  dark  surface  of  the  sea  con- 
tinued without  apparent  interruption  into  that  of 
the  canal.  In  as  much  as  the  surfaces  called  seas 
are  truly  a  liquid  expanse,  we  cannot  doubt  that  the 


SchiaparelWs  Latest  Views  Regarding  Mars     87 

canals  are  a  simple  prolongation  of  them,  crossing 
the  yellow  areas  or  continents. 

Of  the  remainder,  that  the  lines  called  canals  are 
truly  great  furrows  or  depressions  in  the  surface  of 
the  planet,  destined  for  the  passage  of  the  liquid 
mass,  and  constituting  for  it  a  true  hydrographic 
system,  is  demonstrated  by  the  phenomena  which  are 
observed  during  the  melting  of  the  northern  snows. 
We  have  already  remarked  that  at  the  time  of  melt- 
ing they  appeared  surrounded  by  a  dark  zone,  form- 
ing a  species  of  temporary  sea.  At  that  time  the 
canals  of  the  surrounding  region  become  blacker  and 
wider,  increasing  to  the  point  of  converting,  at  a 
certain  time,  all  of  the  yellow  region  comprised  be- 
tween the  edge  of  the  snow  and  the  parallel  of  60° 
north  latitude,  into  numerous  islands  of  small  ex- 
tent. Such  a  state  of  things  does  not  cease,  until 
the  snow,  reduced  to  its  minimum  area,  ceases  to 
melt.  Then  the  breadth  of  the  canals  diminishes,  the 
temporary  sea  disappears,  and  the  yellow  region 
again  returns  to  its  former  area.  The  different 
phases  of  these  vast  phenomena  are  renewed  at  each 
return  of  the  seasons,  and  we  have  been  able  to  ob- 
serve them  in  all  their  particulars  very  easily  during 
the  oppositions  of  1882,  1884  and  1886,  when  the 
planet  presented  its  northern  pole  to  terrestrial 
spectators.  The  most  natural  and  the  most  simple 
interpretation  is  that  to  which  we  have  referred,  of 


88  Mars 

a  great  inundation  produced  by  the  melting  of  the 
snows, — it  is  entirely  logical,  and  is  sustained  by  evi- 
dent analogy  with  terrestrial  phenomena.  We  con- 
clude therefore  that  the  canals  are  such  in  fact,  and 
not  only  in  name.  The  network  formed  by  these  was 
probably  determined  in  its  origin  in  the  geological 
state  of  the  planet,  and  has  come  to  be  slowly  elab- 
orated in  the  course  of  centuries.  It  is  not  necessary 
to  suppose  them  the  work  of  intelligent  beings,  and 
notwithstanding  the  almost  geometrical  appearance 
of  all  of  their  system,  we  are  now  inclined  to  believe 
them  to  be  produced  by  the  evolution  of  the  planet, 
just  as  on  the  Earth  we  have  the  English  Channel 
and  the  Channel  of  Mozambique. 

It  would  be  a  problem  not  less  curious  than  com- 
plicated and  difficult,  to  study  the  system  of  this  im- 
mense stream  of  water,  upon  which  perhaps  depends 
principally  the  organic  life  upon  the  planet,  if  or- 
ganic life  is  found  there.  The  variations  of  their 
appearance  demonstrated  that  this  system  is  not  con- 
stant. When  they  become  displaced,  or  their  out- 
lines become  doubtful  and  ill  defined,  it  is  fair  to  sup- 
pose that  the  water  is  getting  low,  or  is  even  en- 
tirely dried  up.  Then  in  place  of  the  canal  there 
remains  either  nothing,  or  at  most  a  stripe  of  yel- 
lowish color  differing  little  from  the  surrounding 
background.  Sometimes  they  take  on  a  nebulous 
appearance,  for  which  at  present  it  is  not  possible 


Schiaparelli's  Latest  Views  Regarding  Mars      89 

to  assign  a  reason.  At  other  times  true  enlarge- 
ments are  produced,  expanding  to  100,  200  or  more 
kilometers  (60  to  120  miles)  in  breadth,  and  this 
sometimes  happens  for  canals  very  far  from  the 
north  pole,  according  to  laws  which  are  unknown. 
This  has  occurred  in  Hydaspes  in  1864,  in  Simois  in 
1879,  in  Acheron  in  1884,  and  in  Triton  in  1888. 
The  diligent  and  minute  study  of  the  transforma- 
tions of  each  canal  may  lead  later  to  a  knowledge 
of  the  cause  of  these  facts. 

But  the  most  surprising  phenomenon  pertaining 
to  the  canals  of  Mars  is  their  gemination,  which 
seems  to  be  produced  principally  in  the  months  which 
precede,  and  in  those  which  follow,  the  great  northern 
inundation,  at  about  the  times  of  the  equinoxes.  In 
consequence  of  a  rapid  process,  which  certainly  lasts 
at  most  a  few  days,  or  even  perhaps  only  a  few  hours, 
and  of  which  it  has  not  yet  been  possible  to  deter- 
mine the  particulars  with  certainty,  a  given  canal 
changes  its  appearance,  and  is  found  transformed 
through  all  its  length,  into  two  lines  or  uniform 
stripes,  more  or  less  parallel  to  one  another,  and 
which  run  straight  and  equal  with  the  exact  geo- 
metrical precision  of  the  two  rails  of  a  railroad. 
But  this  exact  course  is  the  only  point  of  resem- 
blance with  the  rails,  because  in  dimensions  there  is 
no  comparison  possible,  as  it  is  easy  to  imagine. 
The  two  lines  follow  very  nearly  the  direction  of  the 


90  Mars 

original  canal,  and  end  in  the  place  where  it  ended. 
One  of  these  is  often  superposed  as  exactly  as  pos- 
sible upon  the  former  line,  the  other  being  drawn 
anew,  but  in  this  case  the  original  line  loses  all  the 
small  irregularities  and  curvature  that  it  may  have 
originally  possessed.  But  it  also  happens  that  both 
the  lines  may  occupy  opposite  sides  of  the  former 
canal,  and  be  located  upon  entirely  new  ground.  The 
distance  between  the  two  lines  differs  in  different 
geminations,  and  varies  from  600  kilometers  (360 
miles)  and  more,  down  to  the  smallest  limit  at  which 
two  lines  may  appear  separated  in  large  visual  tele- 
scopes— less  than  an  interval  of  50  kilometers  (30 
miles).  The  breadth  of  the  stripes  themselves  may 
range  from  the  limit  of  visibility,  which  we  may  sup- 
pose to  be  30  kilometers  (18  miles),  up  to  more  than 
100  kilometers  (60  miles).  The  color  of  the  two 
lines  varies  from  black  to  a  light  red,  which  can 
hardly  be  distinguished  from  the  general  yellow 
background  of  the  continental  surface.  The  space 
between  is  for  the  most  part  yellow,  but  in  many 
cases  appears  whitish.  The  gemination  is  not  neces- 
sarily confined  only  to  the  canals,  but  tends  to  be 
produced  also  in  the  lakes.  Often  one  of  these  is 
seen  transformed  into  two  short,  broad,  dark  lines 
parallel  to  one  another,  and  traversed  by  a  yellow 
line.  In  these  cases  the  gemination  is  naturally 


Schiaparelli's  Latest  Views  Regarding  Mars     91 

short,  and  does  not  exceed  the  limits  of  the  original 
lake. 

The  gemination  is  not  shown  by  all  at  the  same 
time,  but  when  the  season  is  at  hand,  it  begins  to  be 
produced  here  and  there,  in  an  isolated  irregular 
manner,  or  at  least  without  any  easily  recognizable 
order.  In  many  canals  (such  as  the  Nilosyrtis,  for 
example)  the  gemination  is  lacking  entirely,  or  is 
scarcely  visible.  After  having  lasted  for  some 
months,  the  markings  jfade  out  gradually  and  dis- 
appear, until  another  season  equally  favorable  for 
their  formation.  Thus  it  happens  that  in  certain 
other  seasons  (especially  near  the  southern  solstice 
of  the  planet),  that  few  are  seen,  or  even  none  at  all. 
In  different  oppositions  the  gemination  of  the  same 
canal  may  present  different  appearances,  as  to  width, 
intensity  and  arrangement  of  the  two  stripes,  also 
in  some  cases  the  direction  of  the  lines  may  vary, 
although  by  the  smallest  quantity,  but  still  deviating 
by  a  small  amount  from  the  canal  with  which  they 
are  directly  associated.  From  this  important  fact 
it  is  immediately  understood  that  the  gemination  can 
not  be  a  fixed  formation  upon  the  surface  of  Mars, 
and  of  a  geographical  character  like  the  canals.  The 
second  of  our  maps  will  give  an  approximate  idea 
of  the  appearance  which  these  singular  formations 
present.  It  contains  all  the  geminations  observed 


92  Mars 

since  1882  up  to  the  present  time.  In  examining  it, 
it  is  necessary  to  bear  in  mind  that  not  all  of  these 
appearances  were  simultaneous,  and  consequently 
that  the  map  does  not  represent  the  condition  of 
Mars  at  any  given  period,  it  is  only  a  sort  of  topo- 
graphical register  of  the  observations  made  at  dif- 
ferent times  of  this  phenomenon.5 

The  observation  of  the  gemination  is  one  of  the 
greatest  difficulty,  and  can  only  be  made  by  an  eye 
well  practiced  in  such  work,  added  to  a  telescope  of 
accurate  construction,  and  of  great  power.  This 
explains  why  it  is  that  it  was  not  seen  before  1882. 
In  the  ten  years  that  have  transpired  since  that 
time,  it  has  been  seen  and  described  at  eight  or  ten 
observatories.  Nevertheless,  some  still  deny  that 
these  phenomena  are  real,  and  tax  with  illusion  (or 
even  imposture)  those  who  declare  that  they  have 
observed  it. 

Their  singular  aspect,  and  their  being  drawn  with 
absolute  geometrical  precision,  as  if  they  were  the 
work  of  rule  or  compass,  has  led  some  to  see  in  them 
the  work  of  intelligent  beings,  inhabitants  of  the 
planet.  I  am  very  careful  not  to  combat  this  sup- 
position, which  includes  nothing  impossible.  (To  mi 
guardero  bene  dal  combattere  questa  supposizione, 
la  quale  nulla  include  d'impossible. )  But  it  will  be 

•This  map  may  be  found  also  in  "La  Planete  Mars,"  by 
Flammarion,  p.  440.— Tr. 


Schiaparetti't  Latett  View*  Regarding  Mart      9$ 

noticed  that  in  any  case  the  gemmation  cannot  be 
a  work  of  permanent  character,  it  being  certain  that 
in  a  given  instance  it  may  change  its  appearance  and 
dimensions  from  one  season  to  another.  If  we  should 
assume  such  a  work,  a  certain  variability  would  not 
be  excluded  from  it,  for  example,  extensive  agricul- 
tural labor  and  irrigation  upon  a  large  scale.  Let 
us  add  further  that  the  intervention  of  intelligent 
beings  might  explain  the  geometrical  appearance  of 
the  gemination,  but  it  is  not  at  all  necessary  for 
such  a  purpose.  The  geometry  of  nature  is  mani- 
fested in  many  other  facts,  from  which  are  excluded 
the  idea  of  any  artificial  labor  whatever.  The  per- 
fect spheroids  of  the  heavenly  bodies  and  the  ring 
of  Saturn  were  not  constructed  in  a  turning  lathe, 
and  not  with  compasses  has  Iris  described  within  the 
clouds  her  beautiful  and  regular  arch.  And  what 
shall  we  say  of  the  infinite  variety  of  those  exquisite 
and  regular  polyhedrons  in  which  the  world  of  crys- 
tals is  so  rich!  In  the  organic  world,  also,  is  not 
that  geometry  most  wonderful  which  presides  over 
the  distribution  of  the  foliage  upon  certain  plants, 
which  orders  the  nearly  symmetrical,  starlike  figures 
of  the  flowers  of  the  field,  as  well  as  of  the  animals 
of  the  sea,  and  which  produces  in  the  shell  such  an 
exquisite  conical  spiral,  that  excels  the  most  beau- 
tiful masterpieces  of  gothic  architecture?  In  all 
these  objects  the  geometrical  form  is  the  simple  and 


94  Mars 

necessary  consequence  of  the  principles  and  laws 
which  govern  the  physical  and  physiological  world. 
That  these  principles  and  these  laws  are  but  an  indi- 
cation of  a  higher  intelligent  power,  we  may  admit, 
but  this  has  nothing  to  do  with  the  present  argu- 
ment. 

Having  regard  then  to  the  principle  that  in  the 
explanation  of  natural  phenomena  it  is  universally 
agreed  to  begin  with  the  simplest  suppositions,  the 
first  hypotheses  on  the  nature  and  cause  of  the  gemi- 
nations have  for  the  most  part  put  in  operation  only 
the  laws  of  inorganic  nature.  Thus,  the  gemination 
is  supposed  to  be  due  either  to  the  effects  of  light 
in  the  atmosphere  of  Mars,  or  to  optical  illusions 
produced  by  vapors  in  various  manners,  or  to  glacial 
phenomena  of  a  perpetual  winter,  to  which  it  is 
known  all  the  planets  will  be  condemned,  or  to 
double  cracks  in  its  surface,  or  to  single  cracks  of 
which  the  images  are  doubled  by  the  effect  of  smoke 
issuing  in  long  lines  and  blown  laterally  by  the  wind. 
The  examination  of  these  ingenious  suppositions 
leads  us  to  conclude  that  none  of  them  seem  to  corre- 
spond entirely  with  the  observed  facts,  either  in  whole 
or  in  part.  Some  of  these  hypotheses  would  not  have 
been  proposed,  had  their  authors  been  able  to  ex- 
amine the  geminations  with  their  own  eyes.  Since 
some  of  these  may  ask  me  directly, — Can  you  sug- 
gest anything  better?  I  must  reply  candidly,  No. 


Schiaparelli's  Latest  Views  Regarding  Mart      95 

It  would  be  far  more  easy  if  we  were  willing  to 
introduce  the  forces  pertaining  to  organic  nature. 
Here  the  field  of  plausible  supposition  is  immense, 
being  capable  of  making  an  infinite  number  of  com- 
binations capable  of  satisfying  the  appearances  even 
with  the  smallest  and  simplest  means.  Changes  of 
vegetation  over  a  vast  area,  and  the  production  of 
animals,  also  very  small,  but  in  enormous  multitudes, 
may  well  be  rendered  visible  at  such  a  distance.  An 
observer  placed  in  the  Moon  would  be  able  to  see 
such  an  appearance  at  the  times  in  which  agricul- 
tural operations  are  carried  out  upon  a  vast  plain, 
— the  seed  time  and  the  gathering  of  the  harvest. 
In  such  a  manner  also  would  the  flowers  of  the  plants 
of  the  great  steppes  of  Europe  and  Asia  be  rendered 
visible  at  the  distance  of  Mars, — by  a  variety  of 
coloring.  A  similar  system  of  operations  produced 
in  that  planet  may  thus  certainly  be  rendered  visible 
to  us.  But  how  difficult  for  the  Lunarians  and  the 
Areans  to  be  able  to  imagine  the  true  causes  of 
such  changes  of  appearance,  without  having  first  at 
least  some  superficial  knowledge  of  terrestrial  na- 
ture! So  also  for  us,  who  know  so  little  of  the 
physical  state  of  Mars,  and  nothing  of  its  organic 
world,  the  great  liberty  of  possible  supposition  ren- 
ders arbitrary  all  explanations  of  this  sort,  and  con- 
stitutes the  gravest  obstacle  to  the  acquisition  of 
well-founded  notions.  All  that  we  may  hope  is  that 


96  Mart 

with  time  the  uncertainty  of  the  problem  will  grad- 
ually dimmish,  demonstrating,  if  not  what  the  gemi- 
nations are,  at  least  what  they  can  not  be.  We  may 
also  confide  a  little  in  what  Galileo  called  "the  cour- 
tesy of  Nature,"  thanks  to  which,  some  time  from 
an  unexpected  source,  a  ray  of  light  will  illuminate 
an  investigation  at  first  believed  inaccessible  to  our 
speculations,  and  of  which  we  have  a  beautiful  ex- 
ample in  celestial  chemistry.  Let  us  therefore  hope 
and  study. 


CHAPTER  VIII 

THE  SEAS  OF  MARS  * 

The  first  observation  made  upon  Mars  at  the 
Lowell  Observatory  with  the  18-inch  Brashear  lens 
was  upon  June  1,  1894*.  Since  then  observations 
have  been  continued  upon  nearly  every  night.  What 
appears  to  me  to  be  the  most  important  conclusion 
deducible  from  our  work  so  far  is  that  Mars  does 
not  always  present  the  same  appearance  at  the  cor- 
responding time  upon  two  successive  Arean  years. 
This  remark  does  not  apply  merely  to  small  details 
but  to  large  and  prominent  features.  Moreover 
this  difference  does  not  seem  to  be  due  simply  to 
the  fact  that  one  season  is  a  few  weeks  later  than 
the  other,  but  that  the  phenomena  presented  upon 
the  two  years  are  really  different. 

Thus  the  central  branch  of  the  Yf,  just  north  of 
Noachis,  which  was  so  marked  a  phenomenon  in 
1892,  was  not  visible  to  me  early  in  June,  as  I  had 
expected  it  to  be.  It  is  true  that  Mr.  Lowell  thought 
he  saw  it  faintly  marked,  but  although  I  looked  for 

1  Astronomy  and  Astro-Physics,  1894, 13,  553. 
fSyrtis  Major. 

97 


98  Mars 

it  upon  the  same  evening,  I  could  not  satisfy  myself 
of  its  existence.  Nevertheless  the  definition  was  such 
that  had  it  appeared  as  it  did  in  1892,  it  could  not 
have  been  missed  at  the  first  glance.  I  looked  for  it 
again  at  the  following  presentation  in  July  just 
passed,  but  no  trace  of  it  was  to  be  seen.  Two  draw- 
ings made  by  Professor  Campbell  upon  July  18 
and  20,  1892,  and  published  in  the  last  number  of 
the  Publications  of  the  Astron.  Soc.  of  the  Pacific, 
p.  171,  show  it  very  nicely  indeed.  These  may  be 
compared  with  some  reproductions  of  my  own  work 
originally  published  in  Astronomy  and  Astro- 
Physics,  1892,  p.  668,  and  now  republished  in  the 
same  number  with  the  drawings  of  Professor  Camp- 
bell. After  the  disappearance  of  the  central  branch 
in  the  latter  part  of  July,  1892,  a  portion  of  it  re- 
appeared in  August,  and  remained  visible  through 
September.  A  sketch  showing  its  appearance  upon 
September  4,  1892,  has  been  kindly  forwarded  to 
me  by  Mr.  Russell  of  the  Sydney  Observatory, 
N.  S.  W.  This  branch  may  therefore  be  said 
to  have  been  characteristic  of  the  opposition  of 
1892.  This  same  region  was  very  carefully  sketched 
by  Mr.  Douglass  and  myself  a  number  of  times 
between  June  30  and  July  6,  1894,  but  not  a  trace 
of  the  central  branch  could  we  detect.  Upon  these 
dates  Mars  held  the  same  position  in  its  orbit 
that  it  did  upon  August  12  and  18,  1892.  A  sketch 


The  Seat  of  Mart  99 

made  by  myself  August  13,  1892,  shows  the  central 
branch  very  clearly.  It  will  be  interesting  to  hear 
if  its  appearance  has  been  noted  this  year  by  the 
Australian  observers,  since  in  their  longitude  it  would 
have  been  visible  about  the  middle  of  June. 

But  not  only  has  the  central  branch  of  the  Y  been 
invisible  this  year,  but  the  large  dark  blue  patch 
which  it  connected  with  the  southern  snow  cap, 
and  which  we  called  the  Northern  Sea,  has  been  very 
much  less  marked,  and  much  smaller  than  was  the 
case  in  1892. 

Again  a  large  black  gulf  bounding  the  melting 
snow  upon  the  north  and  situated  very  nearly  due 
south  of  Syrtis  Minor  has  been  a  very  striking 
feature  of  our  observations  this  year.  This  gulf  was 
only  observed  once  in  1892,  upon  July  27,  and  it  was 
then  by  no  means  conspicuous.  If  these  very  dark 
regions  are,  as  we  suppose  them  to  be,  water,  it 
would  then  seem  that  the  water  which  did  not  reach 
the  northern  regions  this  year  has  appeared  as  an 
excess  in  the  south. 

Upon  testing  this  black  region  upon  June  4,  with 
an  Arago  polariscope,  made  for  me  by  Mr.  Brash- 
ear,  it  was  found  to  show  clear  traces  of  polarization, 
as  did  the  canal  running  north  from  it.  This  would 
naturally  be  the  case  if  it  were  water,  since  being 
situated  near  the  limb,  it  would  reflect  to  us  largely 
the  light  of  the  Arean  atmosphere.  Upon  the  rest 


100  Mars 

of  the  disc  of  the  planet  the  polarization  was  not 
very  conspicuous.  At  the  next  presentation  of  this 
region  upon  July  9,  the  observation  was  repeated, 
but  to  my  surprise  no  trace  of  polarization  in  the 
dark  spot  could  be  detected.  A  close  examination 
of  the  region  was  then  made,  and  its  color  found  to 
have  entirely  changed, — whereas  upon  June  9,  Mr. 
Lowell  writes  "Bay  a  deep  blue,  looks  just  as  deep 
water  does,'*  it  was  now  found  to  be  of  a  rich  choc- 
olate brown  tint,  differing  entirely  in  color  from 
the  bluish  gray  regions  to  the  north  of  it.  These 
gray  regions  showed  no  sign  of  polarization,  and  as 
I  have  before  remarked  I  see  no  reason  for  supposing 
that  their  color  is  due  to  water.  As  far  as  my  ob- 
servations go,  it  appears  to  me  that  the  permanent 
water  area  upon  Mars,  if  it  exists  at  all,  is  extremely 
limited  in  its  dimensions. 

These  large  gray  regions  were  of  a  brilliant  and 
decided  green  color  in  1890,  just  before  the  vernal 
equinox.  In  the  early  part  of  1892  also,  large  green 
areas  were  seen  upon  the  planet,  but  as  the  season 
advanced  the  green  regions  changed  almost  entirely 
to  gray.  At  the  present  time  very  little  color  is 
visible  in  the  shaded  regions.  They  are  subject  also 
to  such  large  variations  in  area,  as  the  season  pro- 
gresses, that  unless  we  can  persuade  ourselves  that 
gigantic  floods,  unaccompanied  by  clouds,  form  the 
normal  condition  of  affairs  upon  Mars,  we  seem 


The  Seas  of  Mars  101 

forced  to  adopt  some  other  explanation  of  their  ex- 
istence. The  theory  that  they  owe  their  color  to 
vegetation  is  perhaps  the  most  plausible  one,  and 
some  new  facts  bearing  upon  this  matter  have  re- 
cently come  to  hand.  Upon  June  30  a  distinct  de- 
pression in  the  terminator  where  it  was  crossed  by 
the  stem  of  the  Y  was  detected  by  Mr.  Douglass. 
As  the  planet  rotated,  the  position  of  the  depres- 
sion changed,  and  it  was  noted  that  it  was  not 
always  found  in  those  portions  of  the  terminator 
which  were  the  darkest.  Since  that  date  similar 
depressions  more  or  less  marked  have  been  detected 
upon  nearly  every  evening.  Upon  looking  over  our 
observations  for  1892,  I  find  under  date  of  Septem- 
ber 20,  8h.  06m.  a  drawing  showing  a  flattened  ter- 
minator, and  a  statement  that  "the  planet  seems 
somewhat  of  this  shape."  Further  investigation 
shows  that  the  long  narrow  strip  known  as  Cerau- 
nius  was  lying  upon  the  terminator  at  about  this 
time.  These  notches  in  the  terminator  can  be  most 
readily  explained  by  actual  depressions  in  the  sur- 
face of  the  planet,  and  as  Professor  Campbell  has 
shown  (Pub.  Astro.  Soc.  Pac.,  1894,  p.  110)  a  dif- 
ference of  elevation  of  the  surface  amounting  to 
two  miles  ought  to  be  readily  visible  to  us  on  the 
Earth  at  certain  seasons  provided  the  elevation  of 
depression  involved  occurred  upon  the  terminator. 
It  thus  appears  that  we  are  perhaps  on  the  eve  of 


103  Mars 

being  able  to  construct  a  contour  map  of  the  planet. 
The  observations  involved  are  however  very  difficult, 
and  no  great  accuracy  in  the  results  can  as  yet  be 
expected. 

Strictly  speaking  the  notches  in  the  terminator 
correspond  to  variations  in  the  inclination  of  the 
surface  of  the  planet  rather  than  to  variations  in 
its  level,  but  if  we  could  determine  the  inclination 
and  knew  the  distance  through  which  it  extended, 
we  should  have  all  the  data  required  for  our  work. 

There  is  one  conclusion  however  to  which  these 
observations  lead  us  at  once.  Since  these  notches 
in  the  terminator  do  not  necessarily  occur  in  the 
darkest  parts  of  the  grey  regions,  and  since  different 
portions  of  them  are  notched  to  different  depths 
when  on  the  terminator,  it  follows  that  all  portions 
of  the  gray  regions  are  not  on  the  same  level.  In 
other  words  hills  and  valleys  occur  in  them,  and 
consequently  the  grey  regions  do  not  represent  the 
surface  of  an  ocean. 


CHAPTER   IX 

RECENT  STUDIES  OF  THE  MARTIAN  AND 
LUNAR  CANALS  1 

It  has  lately  been  shown  by  Messrs.  Lane,  Maun- 
der, and  Evans  that  many  of  the  finer  Martian 
canals  are  probably  nonexistent,  their  appearance 
being  due  to  certain  singular  optical  illusions.  Most 
of  the  broader  canals,  however,  in  the  bright  regions 
of  the  planet,  undoubtedly  exist,  and  the  same  is 
almost  certainly  true  of  the  narrower  ones  in  the 
light  regions,  such  as  Nilosyrtis  and  Nectar.  The 
chief  cause  of  the  illusion  seems  to  be  the  system  of 
lakes,  or  oases  as  they  are  sometimes  called,  which 
were  first  discovered  in  large  numbers  at  Arequipa. 
There  is  a  curious  tendency  of  the  human  eye  to  see 
such  dark  points  united  by  faint  narrow  lines,  and  it 
has  been  shown  by  means  of  diagrams  that  these  lines 
sometimes  appear  when  the  diagram  is  at  such  a 
distance  that  the  dark  dots  are  themselves  invisible. 
But  even  without  the  dots  the  lines  may  sometimes 
appear,  joining  different  portions  of  the  dark 
1  Popular  Astronomy,  1904, 12,  77. 
103 


104.  Mars 

regions.  We  must  therefore  divide  the  Martian 
canals  into  two  classes,  those  that  are  genuine  and 
those  that  are  not. 

Any  canal  that  appears  first  as  a  broad  streak 
of  measurable  breadth,  and  then  gradually  narrows 
as  the  season  progresses  may  be  classed  as  genuine, 
although  its  image  may  appear  by  illusion  long  after 
the  canal  itself  has  really  gone.  This  narrowing  of 
the  canals,  especially  in  the  bright  regions,  is  very 
common  after  the  passage  of  the  vernal  equinox  on 
Mars.  It  is  also  true  of  several  of  the  canals  in 
the  region  about  Solis  Lacus.  Any  canal  on  the  con- 
trary which  suddenly  appears  as  a  faint  narrow 
line  joining  two  dark  regions  may  in  the  future  be 
looked  upon  with  suspicion,  even  if  to  the  trained 
eye  it  is  fairly  well  seen.  To  this  class  perhaps  be- 
long such  conspicuous  and  well-known  examples  as 
Phison,  Gehon  and  Euphrates,  besides  very  many 
other  less  observed  canals. 

This  phenomenon  of  spurious  canals  is  certainly 
very  singular,  but  we  must  be  careful  that  its  in- 
terest and  unexpectedness  do  not  lead  us  into  the 
error  of  affirming  that  because  many  Martian  canals 
are  spurious,  therefore  all  Martian  canals  are 
imaginary.  It  seems  indeed  a  great  pity  that  so 
much  time  and  energy  should  be  expended  in  many 
observatories  in  mapping  canals  in  the  bright  regions 
of  the  planet,  and  comparatively  so  little  time  on 


ERATOSTHENES 


Studies  of  the  Martian  and  Lunar  Canals      105 

the  darker  regions,  where  changes  are  constantly 
taking  place,  and  where  we  should  naturally  expect 
the  most  interesting  developments  to  occur. 

Turning  now  to  the  other  branch  of  our  subject, 
we  find  upon  the  Moon,  where  the  surface  conditions 
are  in  some  respects  similar  to  those  upon  Mars, 
although  the  atmosphere  is  probably  rarer,  numer- 
ous canals,  which  on  account  of  their  proximity  are 
much  more  readily  studied  than  the  Martian  ones. 
While  from  the  Harvard  station  in  Southern  Cali- 
fornia photographs  of  Mars  were  secured  showing 
the  Syrtis  Major,  the  Fastigium  Aryn,  and  other 
prominent  markings,  no  one  has  as  yet  succeeded  in 
photographing  fine  enough  detail  to  show  a  Martian 
canal.  On  the  Moon,  on  the  other  hand,  a  few  canals 
have  already  been  photographed,  both  at  Arequipa 
and  in  Jamaica.  Recently  a  fine  photograph  has 
been  received  through  the  kindness  of  Professor 
Hale,  which  shows  several  of  the  canals  to  much 
better  advantage  than  any  photograph  previously 
taken.  Indeed,  it  may  be  said  that  these  latest  views 
taken  with  the  Yerkes  telescope  show  nearly  all  the 
detail  visible  with  a  6-inch  telescope  working  under 
very  favorable  conditions. 

For  purposes  of  comparison,  I  have  arranged  in 
the  plate  a  drawing  of  the  canals  about  Eratos- 
thenes, made  in  Jamaica,  and  published  in  my  recent 
book  on  the  Moon,  and  an  enlargement  to  the  same 


106  Mars 

scale  of  the  same  region  shown  in  the  Yerkes  photo- 
graph. The  scale  is  gi00Q>000>  or  about  32  miles 
to  the  inch.  The  drawing  was  made  August  1,  1901, 
at  8.6  days  after  sunrise  on  Eratosthenes,  colongi- 
tude  of  the  sunrise  terminator  116°.  The  photo- 
graph was  taken  September  2,  1901,  11.8  days  after 
sunrise,  colongitude  149°.  While  therefore  it  was 
taken  about  three  days  later  in  the  lunation  than 
the  drawing,  still  it  does  not  show  any  very  marked 
changes  to  have  occurred  in  the  meantime,  excepting 
possibly  in  the  relative  intensity  of  some  of  the 
canals.  Since  the  drawing  was  made  only  1.7  days 
after  full  moon,  when  the  sun  was  nearly  in  the 
zenith  of  the  crater,  and  since  the  same  markings  are 
found  on  other  drawings  and  photographs  made  at 
and  before  full  moon,  it  will  be  seen  that  it  is  geo- 
metrically impossible  that  these  markings  should  be 
due  to  shadows.  They  represent  therefore  real  dif- 
ferences in  surface  coloration  and  nothing  else. 

The  other  photograph  is  an  enlargement  from 
the  same  original  negative  to  the  same  scale.  The 
region  shown  is  situated  four  diameters,  south  20° 
west,  from  Eratosthenes.  The  dark  region  at  the 
top  is  in  fact  the  site  of  Gruithuison's  celebrated 
ruined  lunar  city.  He  described  a  central  street  from 
which  five  or  six  parallel  streets  led  off  on  either 
side  at  an  agle  of  45°,  like  the  veins  of  a  leaf. 
Something  of  the  same  sort  has  been  seen  by  several 


REGION    NEAR    ERATOSTHENES 


Studies  of  the  Martian  and  Lwnar  Canals     107 

other  observers,  and  I  have  myself  seen  a  few  of 
the  lines.  The  so-called  streets  are  apparently  a 
difficult  and  very  curious  combination  of  ridges. 
What  interests  us  most,  however,  is  a  series  of  well- 
marked  canals  near  the  center  of  the  view.  Just 
below  the  center  is  a  white  spot.  In  this  is  located 
a  Y-shaped  combination  of  canals.  From  near  the 
foot  of  the  Y  a  canal  leads  off  to  the  right,  to  a 
very  dark  spot.  This  canal  is  fourteen  miles  long, 
and  about  half  a  mile  in  breadth.  A  short  canal 
branches  off  from  its  upper  side,  i.  e.,  towards  the 
south,  and  other  canals  lead  off  from  the  dark  spot. 
Below  and  to  the  left  of  this  spot  is  another  one 
of  about  the  same  size.  Both  are  suspected  of 
changing  the  finer  details  of  their  shape  in  the  course 
of  the  lunation. 

In  my  recent  researches  I  have  found,  and  have 
endeavored  to  show,  that  there  is  a  wealth  of  fine 
detail  upon  the  Moon,  exhibiting  constant  variations, 
of  the  highest  interest  to  the  intelligent  selenog- 
rapher.  Of  these  variations,  many  it  is  believed  are 
periodic,  while  some  are  wholly  irregular  in  their 
character.  To  see  them  does  not  involve  the  use  of  a 
large  telescope,  but  it  does  require  a  good  atmo- 
sphere, and  also  a  knowledge  of  the  kind  of  varia- 
tions one  may  expect  to  observe,  and  of  the  sort  of 
places  in  which  they  are  likely  to  occur.  Without 
this  knowledge  much  time  may  be  wasted  in  study- 
ing unfavorable  localities. 


CHAPTER    X 

AN  EXPLANATION  OF  THE  MARTIAN  AND 
LUNAR    CANALS1 

When  the  suggestion  of  vegetation  was  first 
offered  to  explain  the  so-called  seas  and  canals  of 
Mars,2  the  difficulty  was  strongly  felt  that  while  it 
readily  explained  their  changes  of  area,  shape,  and 
color,  it  did  not  satisfactorily  explain  the  long 
slender  forms  of  the  canals.  That  these  might  be 
due  to  narrow  and  therefore  invisible  water  courses 
was  an  obvious  idea.  Professor  Lowell  in  adopting 
these  views  added  to  them  the  hypothesis  of  an  arti- 
ficial formation.  If  the  canals  were  really  as  straight 
and  uniform  as  they  are  generally  drawn,  it  was 
certainly  hard  to  see  how  they  could  owe  their  origin 
entirely  to  natural  causes.  But  now  that  some  of 
the  English  experimenters,  Messrs.  Lane,  Maunder, 
and  Evans  have  cast  doubt  on  the  existence  of  many 
of  the  straight  canals,  the  hypothesis  of  an  artificial 
origin  is  materially  weakened. 

1  Popular  Astronomy,  1904,  12,  439. 

'  Science,  1888,  12,  89.     Astronomy  and  Astro-Physics,  1892, 
11,  670. 

108 


An  Explanation  of  the  Canals  109 

Another  difficulty  which  early  presented  itself 
was  to  explain  what  caused  the  water  to  flow  through 
the  narrow  channels,  unless  we  supposed  it  was  arti- 
ficially pumped  through  them.  This  has  always 
seemed  to  the  writer  to  be  the  chief  difficulty  with 
the  whole  explanation,  but  Professor  Lowell  has 
now  courageously  taken  the  bull  by  the  horns,  and 
adopted  the  pumping  hypothesis.3  If  the  surface 
is  level,  gravity  would  not  come  into  the  question, 
but  we  may  well  ponder  upon  the  amount  of  energy 
transformed  into  work  which  could  furnish  enough 
water  to  irrigate  anywhere  from  a  hundred  thou- 
sand to  a  few  million  square  miles  of  surface. 

When  the  canals  on  the  Moon  were  discovered, 
it  was  thought  that  they  might  throw  some  light 
upon  this  puzzling  question.  It  must  be  remembered 
that  the  Moon  is  about  200  times  nearer  than  Mars 
at  an  average  opposition,  and  we  can  readily  imag- 
ine that  if  we  could  increase  the  power  of  our  tele- 
scopes 200  times,  we  might  make  quite  a  number  of 
interesting  discoveries  upon  Mars. 

Upon  the  Moon  as  upon  that  planet,  several 
canals  frequently  radiate  from  a  single  lake,  but 
what  was  most  unexpected,  the  lakes  are  sometimes 
found  at  the  bottom  of  a  lunar  valley,  and  sometimes 
upon  the  crest  of  a  crater  wall.  As  is  the  case  with 
Mars  also,  when  the  sun  rises  upon  them,  and  the 

*  Proceedings  Amer.  Philosophical  Society,  1903,  42,  364. 


110  Mart 

snow  melts,  the  lakes  and  canals  develop  and  become 
conspicuous,  subsequently  fading  out  at  sunset, 
which  corresponds  to  the  Martian  winter. 

It  has  been  shown 4  that  in  the  lunar  crater 
Alphonsus  there  are  eight  variable  spots,  or  lakes 
as  we  should  now  call  them.  In  the  exact  center  of 
each,  excepting  the  largest  one,  is  found  a  minute 
craterlet.  In  the  largest  lake  there  are  two  large 
craterlets  and  five  small  ones.  The  canals  radiate 
from  the  lakes  and  therefore  from  these  craterlets. 
The  symmetrical  arrangement  of  the  lakes  about  the 
craterlets  in  so  many  instances  indicates  a  causal 
relation  between  them,  and  that  the  vegetation  of 
the  lake,  if  such  it  be,  owes  its  origin  to  some  vol- 
canic action. 

In  the  case  of  several  of  the  large  craters,  notably 
Tycho,  we  find  a  similar  radiating  structure,  and 
in  the  case  of  Tycho  even  a  dark  spot  or  halo  at 
the  center.  In  this  case  the  whole  formation  is  upon 
so  large  a  scale  that  its  elementary  structure  can 
be  clearly  distinguished.  The  white  radiating  lines 
or  bands  are  seen  to  be  due  to  numerous  minute 
craterlets,  each  giving  out  a  triangular  white 
streamer,  the  alignment  of  these  streamers  producing 
the  general  effect  of  a  white  band.  It  is  probable 
that  this  observed  regular  distribution  of  the  crater- 
lets  is  due  to  their  lying  along  invisible  cracks  radiat- 

4  Harvard  Annals,  32,  99. 


An  Explanation  of  the  Canalt  111 

ing  from  the  main  crater.  It  is  much  the  same  as 
the  great  volcanoes  of  the  Andes,  which  stretch  in 
a  straight  line  for  over  2,000  miles  between  Peru 
and  the  Straits  of  Magellan.  The  Alaskan  volcanoes 
lie  upon  a  uniformly  curved  line  of  nearly  equal 
length.  Most  of  the  terrestrial  volcanoes  are  dis- 
tributed along  similar  lines.  This  line  formation  is 
generally  considered  by  geologists  to  be  due  to  sub- 
terranean lines  of  weakness  or  cracks  in  the  earth's 
crust.  Such  being  the  case,  it  seems  probable  that 
the  canals  on  the  Moon  lie  along  similar  invisible 
cracks  radiating  from  the  small  craterlet  at  the 
center  of  each  lake.  These  cracks  are  not  always 
straight  but  such  is  their  general  tendency.  Under 
favorable  illumination  small  cracks  are  found  to  be 
very  common  upon  the  surface  of  the  Moon,  and  in 
the  cases  of  Petavious,  Alphonsus,  and  Atlas  that 
class  of  cracks  that  we  have  designated  from  their 
shape  as  river-beds  are  seen  to  be  intimately  asso- 
ciated with  the  lakes  and  canals.5  It  is  believed 
that  enough  water  vapor  and  carbonic  acid  escape 
from  the  central  craterlet  and  flow  down  its  sides 
to  develop  the  vegetation  upon  its  slopes,  and  that 
the  smaller  quantities  escaping  from  various  points 
along  the  radiating  cracks  similarly  develop  the 
vegetation  which  shows  along  their  sides.  In  addi- 
tion to  the  escaping  vapor,  water  itself  might  issue 
'  Harvard  Annals,  32,  98  and  113,  sec  also  Plate  VII. 


112  Man 

from  the  subterranean  crack  and  percolating 
through  the  soil  be  evaporated  from  its  surface. 

It  is  not  thought  that  there  is  any  transfer  of 
vapor  lengthwise  of  the  crack  but  that  on  account 
of  the  lack  of  external  atmospheric  pressure  the 
vapor  rises  quietly  directly  from  the  lower  regions, 
owing  to  the  internal  heat  of  the  Moon.  As  soon  as 
the  exterior  is  sufficiently  warmed  by  the  sun,  the 
vapor  and  gas  would  begin  to  appear.  On  account 
of  the  rarity  of  the  atmosphere,  instead  of  rising 
they  would  immediately  spread  themselves  along  the 
surface  of  the  ground.  Even  in  desert  regions  upon 
the  Earth  we  should  therefore  scarcely  expect  to 
find  similar  formations  unless  actually  irrigated  by 
water,  instead  of  water  vapor.  In  its  physical  con- 
dition Mars  seems  to  occupy  an  intermediate  posi- 
tion between  the  Earth  and  the  Moon. 

It  seems  to  the  writer  that  the  merit  of  this  ex- 
planation lies  not  so  much  in  its  novelty,  but  rather 
because  it  is  founded  so  largely  upon  observed  facts. 


CHAPTER  XI 
THE  DOUBLE  CANALS  OF  MARS  * 

A  few  years  ago  the  doubling  of  the  Martian  canal 
system  was  generally  admitted  by  astronomers  as  an 
accepted  fact.  Latterly  however  doubts  have  begun 
to  arise  with  regard  to  it.  It  was  shown  by  the 
writer,  in  the  Harvard  Annals  XXXII,  149,  that 
accepting  the  results  of  Schiaparelli,  Flammarion, 
Antoniadi  and  Lowell,  the  double  canals  had  this 
curious  property,  namely,  that  their  linear  separa- 
tion was  inversely  proportional  to  the  diameter  of 
the  object-glass  of  the  telescope,  and  directly  pro- 
portional to  the  distance  of  the  planet. 

It  was  then  suggested  that  some  one  who  was 
able  to  see  the  duplication  of  the  canals,  which  the 
writer  has  never  been  able  to  do,  should  make  meas- 
ures of  their  separation,  using  different  apertures 
in  front  of  the  telescope  upon  the  same  night.  This 
has  now  been  done  by  Professor  Lowell,  Bulletin  5, 
Lowell  Observatory,  and  a  recent  examination  of 
his  work,  has  shown  that  he  has  brought  out  some 
very  instructive  results. 

1  Popular  Astronomy,  1904,  12,  385. 
113 


114  Mars 

In  the  first  place  as  far  as  he  is  concerned  it  is 
evident  that  the  separation  of  the  canals  is  inde- 
pendent of  the  aperture  of  the  telescope  employed. 
Secondly,  he  has  found  that  the  duplication  of  the 
canals  can  be  seen  with  surprisingly  small  apertures. 
Thus  with  six  inches  he  divides  the  three  double 
canals  Euphrates,  Hiddekel,  and  Gihon  when  their 
components  were  separated  only  0".27,  0".26,  and 
0".28  respectively. 

It  was  found  by  Dawes  that  an  objective  one 
inch  in  diameter  could  separate  (not  merely  elon- 
gate) two  equal  stars  4".56  apart.  A  ,6-inch  objec- 
tive should  therefore  separate  stars  at  one-sixth 
this  distance,  or  0".76.  Experiments  made  at  Cam- 
bridge with  a  15-inch  aperture  Harvard  Annals 
XXXII,  149,  showed  that  in  order  to  divide  two 
lines  drawn  in  ink  on  white  paper,  they  must  be 
separated  by  an  angle  of  0".42.  For  a  6-inch  objec- 
tive the  required  separation  would  therefore  be 
1".05. 

An  analogous  experiment  may  be  readily  repeated 
without  instruments.  Draw  two  lines  in  ink  1  milli- 
meter, or  one  twenty-fifth  of  an  inch  apart,  on  white 
paper.  Placed  at  a  distance  of  ten  feet  they  can 
just  be  divided  with  the  naked  eye.  Their  separation 
will  be  70".  The  diameter  of  the  pupil  of  the  eye 
in  a  brightly  lighted  room  is  about  one-tenth  of  an 
inch.  If  we  can  conceive  the  pupil  enlarged  sixty 


The  Double  Canals  of  Mart  115 

times,  which  is  what  is  practically  done  by  a  6-inch 
telescope,  we  should  be  able  to  separate  the  lines  at 
one-sixtieth  of  this  distance  apart,  or  at  1".15. 

Summarizing  our  results,  and  applying  them  to 
the  case  of  a  6-inch  telescope,  we  find  from  Da>ve*' 
experiments,  confirmed  universally  by  astronomers, 
that  two  stars  could  only  be  separated  when  as 
much  as  0".76  apart.  The  less  the  contrast  the 
more  difficult  the  separation.  Therefore  for  black 
lines  on  white  paper  we  need  a  greater  separation 
than  in  the  case  of  the  stars.  Our  telescopic  experi- 
ments with  black  lines  indicate  that  the  angle  must 
measure  1".05.  Our  naked  eye  experiments  make 
the  angle  1".15.  In  the  case  of  Mars,  Professor 
Lowell  can  detect  the  duplication  when  the  separa- 
tion is  only  0".&6.  This  would  be  equivalent  in  the 
case  of  the  naked  eye  experiment  to  separating  two 
lines  one  millimeter  apart  at  a  distance  of  forty 
feet.  This  the  reader  will  find  is  quite  impossible. 

The  writer  hesitates  to  believe  that  Professor 
Lowell  can  separate  two  actual  lines  which  are  so 
much  nearer  together  than  the  limit  for  other  ob- 
servers, and  thinks  therefore  that  what  he  sees 
must  be  some  optical  illusion. 


CHAPTER  XII 
THE  EXPECTED  MARTIAN  SNOWS  l 

It  may  interest  observers  to  know  that  ice  will 
probably  begin  to  form  at  both  poles  of  Mars  during 
the  month  of  April.  The  north  pole  will  be  turned 
toward  the  Earth  at  an  angle  of  from  10°  to  1S° 
during  the  month,  and  the  meteorological  changes 
that  we  may  expect  to  see  when  the  ice  appears 
should  be  quite  conspicuous,  the  northern  ice  melting 
rapidly  in  the  continuous  sunshine.  The  poles  may 
appear  either  a  pure  white,  a  light  yellow  or  a  bright 
but  vivid  green.  The  first  indicates  hoar  frost  or 
snow,  the  second  clouds,  and  the  third,  at  least  in 
part,  vegetation.  The  green  over  a  considerable 
portion  of  the  planet  will  be  particularly  vivid  dur- 
ing the  present  opposition,  and  should  be  visible 
even  in  small  telescopes.  A  paper  on  Martian  Mete- 
orology is  now  in  preparation  for  the  Harvard  An- 
nals treating  this  subject  in  more  detail,  but  it  prob- 
ably will  not  be  ready  for  distribution  before  sum- 
mer. 

1  Popular  Astronomy,  1905,  13,  196. 
116 


The  Martian  Snows  117 

The  planet  will  be  from  13"  to  17"  in  diameter, 
coming  to  opposition  early  in  May,  so  that  the  disc 
will  be  large  enough  to  be  well  seen.  Indeed,  this 
opposition  will  be  particularly  favorable  to  these 
observations,  the  planet  being  nearer  us  and  better 
placed  during  this  portion  of  its  year,  than  during 
either  the  preceding  or  following  oppositions.  It  is 
unfortunately  rather  far  to  the  south,  declination 
— 18°,  and  observations  at  the  beginning  of  the 
month  cannot  be  made  much  before  midnight, — 
meridian  passage  14h.  53m.  By  the  end  of  the  month 
observations  may  begin  shortly  before  ten  o'clock, 
— meridian  passage  l£h.  39m. 

OBSERVED 

In  the  April  number  of  Popular  Astronomy  atten- 
tion was  called  to  this  planet,  and  the  opinion  ex- 
pressed that  the  polar  caps  should  appear  during 
the  month.  Owing  to  the  press  of  other  matters  it 
was  not  possible  to  maintain  visual  observations  in 
Cambridge,  but  photographs  were  obtained  under 
the  direction  of  Mr.  King  with  the  11-inch  Draper 
telescope  whenever  practicable.  An  enlarging  lens 
was  employed,  giving  the  original  negative  on  a  scale 
of  about  2. "5  to  the  millimeter. 

The  first  photograph  was  taken  upon  March  31, 


118  Mars 

others  being  secured  upon  April  1,  2,  8,  15,  16,  18, 
23,  25,  27,  and  30.  The  first  photograph  showed 
clouds  at  both  the  limb  and  terminator,  but  no  polar 
caps  properly  so-called  appeared  until  April  23, 
when  a  large  light  area  was  clearly  visible  at  the 
south  pole.  It  did  not  appear  bright  enough  for 
snow,  however,  but  more  resembled  an  extensive 
cloudy  region.  It  has  remained  visible  upon  the 
photographs  since  that  date,  although  with  slightly 
diminished  intensity  and  size.  A  minute  bright  area 
appeared  near  the  north  pole  on  April  15,  but  was 
seen  only  with  difficulty. 

A  visual  examination  of  Mars  was  made  on  the 
night  of  April  30,  with  the  24-inch  reflector.  The 
southern  polar  cap  was  clearly  visible,  extending 
far  to  the  north  in  longitude  340°,  but  its  inten- 
sity was  slight,  little  exceeding  that  of  the  limb  in 
other  regions.  It  is  probable  that  when  the  Mar- 
tian clouds  clear  away,  snow  will  be  found  lying  in 
their  place. 

The  heliocentric  colongitudes  of  the  planet  upon 
April  15  and  23  were  216°  and  220°.  These  posi- 
tions would  correspond  on  the  Earth  to  August  3 
and  7,  or  to  near  the  end  of  the  winter  of  the  south- 
ern hemisphere.  Snow  seldom  comes  earlier  upon 
Mars.  Extensive  green  areas  should  be  visible  in 
June,  and  the  Mare  Erythraeum  recently  described 


The  Martian  Snows  119 

by  Professor  Lowell  as  brown,  should  by  that  time 
have  recovered  its  normal  color.  This  change  of 
color  with  the  seasons  seems  to  the  writer  the  best 
proof  of  the  existence  of  vegetation  on  Mars. 


CHAPTER  XIII 
WHAT  WE  KNOW  ABOUT  MARS  x 

During  the  next  three  years  the  planet  Mars  will 
twice  approach  nearer  to  the  Earth  than  has  been 
the  case  since  1892.  It  will,  therefore,  be  a  very 
conspicuous  object  in  the  heavens,  equaling  Jupiter 
in  brilliancy,  and  will  excite  considerable  attention 
from  astronomers  in  various  parts  of  the  world. 

THE   ORBIT   OF   MARS 

To  understand  why,  unlike  the  case  of  the  other 
planets,  these  near  approaches  occur  only  at  such 
long  and  irregular  intervals,  let  us  imagine  the  larger 
circle  (Fig.  1)  to  represent  the  orbit  of  Mars,  and 
the  smaller  one  the  orbit  of  the  Earth,  the  Sun  being 
at  S.  These  orbits  are  not  really  circles,  but  ellipses, 
the  Sun  being  a  little  to  one  side  of  the  exact  cen- 
ter in  each  case.  The  intersections  of  the  two  in- 
clined diameters  P  A,  pa,  with  the  orbits,  show  where 

1  The  Technical  World  Magazine,  1906,  460. 
120 


What  We  Know  About  Mars 


the  planets  are  nearest  and  farthest  from  the  Sun. 
When  Mars  is  nearest  the  Sun  it  will  be  seen  that 
the  Earth  is  nearly  at  its  greatest  distance,  which 
brings  the  two  orbits  closer  together  there  than 
elsewhere. 

The  Earth  moves  in  its  orbit  much  faster  than 
Mars,  and  also  has  a  shorter  distance  to  travel;  it 
therefore  overtakes  Mars  once  in  a  little  over  two 
years.  When  this  is  the  case,  the  two  planets  are 
much  nearer  together  than  at  other  times.  Mars 
then  rises  just  at  sunset;  and  since  it  is  in  the  op- 

90* 


180* 


WO* 

Fio.  1.    ORBITS  OF  THE  EARTH  AND  MASS 


122  Mart 

posite  part  of  the  sky  to  the  Sun,  it  is  said  to  be 
in  opposition.  In  the  figure,  the  short  lines  con- 
necting the  two  orbits  show  where  the  different  op- 
positions have  occurred.  In  that  of  1892,  the  two 
planets  were  very  near  together;  in  1894  they  were 
somewhat  farther  apart;  but  no  favorable  opposi- 
tion has  occurred  since  then.  The  next  one  will  take 
place  in  1907,  and  will  be  a  little  better  than  that 
of  1894.  The  distance  of  Mars  from  the  Earth  will 
then  be  38,200,000  miles,  while  the  shortest  possible 
distance  is  35,000,000  miles.  The  most  favorable 
oppositions  occur  in  the  latter  part  of  August. 

The  parts  of  the  Martian  orbit  marked  n  and  s 
in  the  figure,  show  when  the  planet's  poles  are  pointed 
most  nearly  towards  the  Sun.  Thus  at  s  is  the  south- 
ern summer  and  northern  winter.  Since  the  planet 
is  here  so  much  nearer  the  Earth  than  at  n,  it  is  pos- 
sible for  us  to  see  the  details  of  its  southern  hemi- 
sphere very  much  better  than  we  ever  can  those  of 
its  northern  one. 

The  inclination  of  the  equator  of  Mars  to  its  or- 
bit is  24°,  or  about  the  same  as  that  of  the  Earth. 
The  seasons  on  the  two  planets  are  therefore  iden- 
tical, except  that,  on  account  of  the  longer  year, 
those  on  Mars  are  twice  as  long  as  our  own.  The 
Martian  day  is  about  forty  minutes  longer  than 
ours. 


What  We  Know  About  Mars  123 


GRAVITATION,    WATER,    AND    ATMOSPHERE 

The  diameter  of  Mars  is  4,200  miles,  or  a  little 
over  half  that  of  the  Earth.  Its  mass,  or  the  amount 
of  matter  it  contains,  is  0.12  as  compared  with  that 
of  the  Earth;  and  the  force  of  gravity  at  its  sur- 
face, 0.38,  or  about  two-fifths  that  at  the  surface 
of  the  Earth.  A  man  weighing  150  pounds  on  the 
Earth  would  weigh  rather  less  than  60  pounds  on 
Mars,  and  could  accordingly  be  much  more  active. 
He  could  jump  much  higher  and  throw  a  stone  two 
and  a-half  times  as  far.  It  will  be  noticed  that  he 
could  not  move  the  stone  any  faster  than  he  could 
upon  the  Earth;  merely,  it  would  take  longer  to 
fall,  and  therefore  would  go  farther  before  striking 
the  ground. 

The  effect  of  this  small  constant  of  gravitation 
has  a  most  important  influence  on  the  physical  con- 
ditions at  the  surface  of  Mars.  Bodies  where  this 
constant  is  large,  like  the  Sun  and  stars,  can  re- 
tain enormous  atmospheres  of  the  lighter  gases,  like 
hydrogen  and  helium,  which  escape  at  once  into  outer 
space  from  the  Earth's  atmosphere.  Bodies  where 
the  constant  is  small,  like  our  Moon,  lose  nearly 
all  their  atmosphere,  save  such  components  as  are 
being  constantly  liberated  from  their  interior,  like 


Mars 

water  vapor  and  carbonic  acid.  Mars,  where  the 
constant  of  gravitation  lies  between  those  of  the 
Earth  and  Moon,  must  have  an  atmosphere  inter- 
mediate in  its  density  and  composition.  That  its 
atmosphere  contains  water  vapor,  we  know,  because 
we  see  it  frozen  at  its  poles  in  the  form  of  ice,  and 
later  melted  to  form  water.  It  is  sometimes  sug- 
gested that  this  white  material,  which  increases  in 
winter  and  diminishes  in  summer,  may  be  carbonic 
acid;  but  this  cannot  be  the  case,  since  carbonic 
acid  does  not  become  liquid  at  pressures  of  less  than 
five  atmospheres,  no  matter  what  the  temperature 
may  be.  The  atmosphere  of  Mars,  we  know,  is  very 
rare;  therefore  the  liquid  we  see  surrounding  the 
melting  ice-caps  cannot  be  carbonic  acid.  There  is 
no  substance  known,  save  water,  that  would  meet 
these  conditions ;  therefore,  if  the  polar  caps  of  Mars 
are  not  due  to  ice,  they  must  be  caused  by  some 
substance  that  is  not  found  upon  the  earth — which 
conclusion  is  improbable. 

Water  is  nevertheless  very  scare  on  Mars ;  and  its 
oceans,  if  it  has  any,  are  shallow  and  only  tempo- 
rary, existing  solely  at  the  times  of  the  spring 
freshets.  In  Fig.  2  is  shown  the  south  polar  cap 
after  the  ice  has  begun  to  melt.  Below,  and  to  the 
right  of  it,  is  seen  a  very  dark  area,  which  the  polari- 
scope  shows  differs  from  the  rest  of  the  planet  in 


Showing   White    Polar    Cap.      From 
drawing  by  the  writer 


FIG.  3.  REGION  ABOUT 
SYRTIS  MINOR,  SHOWING 
SOME  SHORT  AND  EXTREMELY 

NARROW   CANALS 

A  lake  near  center  of  one  of  the 

seas    is    also    shown,    just   above 

center    of    the    figure.      From    a 

drawing  by  the  writer  in  1894 


FIG.    4.       PHOTOGRAPH    OF    MARS    TAKEN    AT    HARVARD    OB- 
SERVATORY AND  THE  HARVARD  STATION  ON  MOUNT  WILSON 
IN   SOUTHERN   CALIFORNIA    IN    1888   AND    1890 


What  We  Know  About  Mars  125 

that  it  has  a  shiny  surface.2  In  the  springtime, 
shortly  after  the  ice  has  begun  to  melt,  this  dark 
area  forms  a  ring  surrounding  the  ice,  measuring 
some  two  thousand  miles  in  diameter  and  in  some 
places  over  two  hundred  miles  in  breadth.  As  the 
ice-cap  diminishes  in  size,  the  black  border  retreats 
with  it  towards  the  pole.  This  leads  us  to  believe 
that  the  black  area  is  due  to  a  swamp  or  a  collection 
of  swampy  pools  and  streams,  rather  than  a  sea. 
Within  the  ice-cap  is  seen  a  lake  connected  with  the 
swamp  by  a  narrow  strait. 

If  the  ice-cap,  when  at  its  maximum  size,  contains 
the  larger  part  of  the  total  water  supply  of  the 
planet,  it  will  not  be  difficult  to  form  an  idea  of  its 
volume.  Let  us  assume  that  the  mean  depth  melted 
by  our  Sun  in  four  of  our  months  over  the  whole 
area  is  twenty  feet,  and  that  the  ice  has  the  con- 
sistency of  snow.  This,  when  melted,  would  give  us 
a  lake  2,000  miles  in  diameter  and  two  feet  in  depth. 
This  would  be  about  the  amount  of  water  con- 
tained in  one  of  our  great  lakes.  One  thousand 
times  this  amount  would  be  insignificant  compared 
to  our  terrestrial  oceans. 

Probably  water  would  not  now  be  found  on  the 
planet  at  all,  if,  as  in  the  case  of  our  Moon,  it  were 
not  constantly  renewed  from  the  interior.  Fresh 

9  Astronomy  and  Astro-Physics,  1894,  13,  554. 


126  Mart 

supplies  are  thus  gradually  taking  the  place  of  that 
which  is  being  slowly  dissipated  into  space.  Sooner 
or  later  these  supplies  must  be  exhausted ;  and  then, 
if  not  before,  all  life  on  both  these  bodies  must  cease. 
On  our  Earth  too,  when  our  volcanoes  cease  to  evolve 
carbonic  acid,  plant  life,  and  with  it  all  animal  life, 
must  necessarily  come  to  an  end. 

Oxygen  and  nitrogen  may  exist  upon  Mars,  but 
probably  in  small  quantities.  Campbell  has  shown 
by  spectroscopic  evidence,  that  the  density  of  the 
Martian  atmosphere  cannot  exceed  one-quarter  that 
of  our  own,  and  is  probably  much  less.  The  exist- 
ence of  water  in  the  liquid  form  shows  that  the  den- 
sity of  the  Martian  atmosphere  must  exceed  1-150 
that  of  the  Earth.  As  far  as  we  know  at  present, 
therefore,  the  equivalent  pressure  of  the  Martian  at- 
mosphere is  less  than  7.5  inches,  and  is  more  than 
0.2  inch.  The  light  and  absorption  visible  at  the 
bright  edge  of  Mars  indicate  that  the  true  value 
lies  nearer  to  the  upper  of  these  limits  than  it  does 
to  the  lower  one.  The  lowest  pressure  at  which 
man  can  live,  as  shown  by  recent  experiments  made 
by  inhaling  oxygen  and  carbonic  acid  combined,  is 
about  5  inches;  and  that  is  probably  only  for  a 
short  time;  but  doubtless  an  intelligent  race  might 
be  slowly  evolved,  capable  of  sustaining  life  at  still 
lower  pressures. 


What  We  Know  About  Mart  1S7 


CLIMATE    AND    METEOROLOGY 

The  fundamental  fact  on  which  we  must  base  our 
knowledge  of  the  climate  of  Mars,  is  the  melting  of 
its  polar  snows.  Where  these  are  melting,  the  tem- 
perature must  be  32°  F. ;  and  nearer  the  equator 
it  must  be  warmer.  The  climate  of  the  Earth  is 
tempered  by  our  great  oceans.  Otherwise  our  sum- 
mers would  be  much  hotter,  and  our  winters  much 
colder.  In  the  heart  of  the  continents,  the  extremes 
are  much  greater  than  on  the  coast.  On  Mars, 
where  there  are  no  permanent  oceans,  the  extremes 
must  be  greater  still.  Our  atmosphere  also  serves 
to  moderate  our  climate.  On  high  mountain  sum- 
mits, the  extremes  are  much  greater  than  at  sea- 
level.  The  comparatively  rare  atmosphere  of  Mars 
must  be  of  little  use  in  this  respect. 

Certain  causes  tend  to  raise  the  mean  temperature 
of  Mars.  The  relatively  large  amount  of  cloud  and 
illuminated  snow  areas  of  the  Earth,  cause  a  great 
waste  of  heat  by  reflection,  which  does  not  occur 
upon  Mars.  If  the  nights  of  Mars  are  compara- 
tively cloudy,  as  may  be  the  case,  these  clouds  would 
help  to  projfcect  the  planet  from  radiation  into  space 
during  that  portion  of  the  Martian  day,  and  thus 
also  tend  to  raise  its  temperature. 


128  Mart 

In  the  summer  season,  on  account  of  the  rare 
atmosphere  and  the  lack  of  water,  the  arctic  re- 
gions on  Mars  must  enjoy  a  temperature  but  little 
lower  than  that  of  the  torrid  zone,  but  during  the 
long  winter  night  the  polar  cold  must  be  intense, 
and  but  little  removed  from  absolute  zero — that  is 
— 4*60°  F.  As  to  the  highest  temperature  experi- 
enced on  Mars,  we  have  no  information,  but  may 
suppose  it  to  be  inferior  to  that  found  upon  the 
Earth.  In  the  torrid  zone,  humanity  would  possibly 
find  the  range  of  temperature  disagreeable,  but  prob- 
ably not  unbearable.  Even  in  the  polar  regions, 
vegetation,  if  not  animal  life,  might  exist,  much  as  it 
does  with  us. 

The  clouds  of  Mars  for  some  unknown  reason  ap- 
pear yellowish  in  color.  On  the  surface  of  the  disc, 
although  visible,  they  are  not  conspicuous,  but  can 
readily  be  photographed.  On  the  terminator  they 
are  at  certain  seasons  easily  seen.  In  the  opposition 
of  1894,  many  were  recorded  at  Flagstaff.  The  pro- 
jection on  the  left-hand  side  of  Fig.  3  is  due  to  cloud. 
Only  three  clouds  are  on  record  which  could  be  iden- 
tified upon  two  successive  nights.  These  all  were 
discovered  at  Flagstaff,  and  were  seen  in  the  years 
1894,3  1900,4  and  1903.5  They  appeared  in  what 

•Astro-Physical  Journal,  1895, 1,  127;  also  "Mars,"  P.  Lowell, 
70. 

*  Proceedings,  American  Philosophical  Society,  No.  167,  page 
166. 

•Lowell  Observatory  Bulletin  No.  1. 


What  We  Know  About  Mars  129 

would  correspond  to  the  late  summer  or  autumn  upon 
the  planet,  two  within  and  one  near  the  borders  of 
the  torrid  zone,  all  within  60°  of  the  Sinus  Sabaeus. 
They  were  all  three  at  an  altitude  of  about  fifteen 
miles,  and  moved  in  a  general  northwesterly  direc- 
tion, with  velocities  of  from  13  to  27  miles  per  hour. 
These  altitudes  are  much  greater  than  those  of  ter- 
restrial clouds,  while  the  velocities  indicate  a  com- 
paratively sluggish  atmospheric  circulation,  which 
is  what  we  should  expect. 

The  nine  photographs  shown  in  Fig.  4  are  the  first 
ones  ever  taken  showing  detail  upon  Mars.  Draw- 
ings and  photographs  of  the  planets  are  always 
turned  so  that  south  shall  be  at  the  top.  The  right- 
hand  side  is  called  east.  The  bright  edge  is  called 
the  "limb" ;  the  dark  edge,  which  is  where  the  Sun  is 
rising  or  setting,  is  called  the  "terminator." 

The  first  photograph  shows  the  equatorial  cloud- 
band.  The  second  shows  the  north  polar  cap.  The 
third  was  taken  the  next  day,  and  shows  the  forma- 
tion during  the  twenty-four  hours  of  a  new  south 
polar  cap.  The  fourth  was  taken  five  days  later, 
and  shows  the  increase  in  size  of  this  cap.  The  fifth 
photograph  shows  the  cap  well  developed,  also  a 
faint  equatorial  cloud-belt,  and  below  it  one  of  those 
mysterious  white  spots  which  are  never  found  far 
from  the  equator.  Unlike  the  clouds,  these  spots  do 
not  change  their  position,  but  persist  for  long  pe- 


130  Mart 

riods  of  time.  This  one  was  still  visible,  although 
faint,  at  the  end  of  six  weeks.  There  are  no  moun- 
tains on  Mars  to  collect  clouds,  save  possibly  a  short 
range  near  the  south  pole.  It  does  not  seem  likely 
that  this  spot  was  due  either  to  ice  or  to  clouds.  It 
was  located  near  the  Trivium  Charontis,  in  longi- 
tude 205°,  latitude  -\-  15°.  A  similar  though  less 
conspicuous  white  spot  had  been  observed  on  the 
equator  in  longitude  300°,  in  1892,  at  Arequipa,  and 
in  1901  and  1903  at  Flagstaff.  The  spot  near  the 
Trivium  is  visible  only  during  the  summer  season  on 
Mars,  its  first  recorded  equivalent  date  of  visibility 
being  June  2,  and  the  last  September  13.  It  is  pos- 
sibly due  to  vegetation.  If  so,  it  is  perhaps  appro- 
priate that  Schiaparelli  should  have  designated  this 
region  under  the  name  "Elysium." 

The  ninth  photograph  shows  the  decreasing  size 
of  the  southern  ice-cap,  while  a  temporary  belt  of 
cloud  surrounding  the  north  pole  is  also  shown.  A 
study  of  photographs  like  these  enables  us  to  deter- 
mine the  duration  of  the  cloudy  and  clear  spells  upon 
Mars.  Continuous  cloudy  weather  near  the  equator 
or  tropics  is  very  rare,  but  in  the  polar  regions  the 
clouds  frequently  last  for  weeks  at  a  time.  The  in- 
tervening periods  of  clear  weather  are  also  of 
long  duration.6  The  three  remaining  photographs 
show  permanent  details  upon  the  disc.  The  dark 

•Annals,  Harvard  College  Observatory,  53,  165. 


What  We  Know  About  Mars  181 

spot  just  above  the  middle  of  the  sixth  view  is  the 
Sinus  Sabseus,  from  which  Martian  longitudes  are 
reckoned.  The  dark  spot  on  the  two  others  is  the 
Syrtis  Major. 


SEAS,  CANALS,  AND  LAKES 

The  first  drawing  ever  made  of  a  dark  area  or  sea 
on  Mars  was  of  this  same  Syrtis  Major,  by  Huygens, 
in  1659.  The  first  map  showing  a  canal  and  lake 
was  constructed  by  Beer  and  Maedler  in  1840.  The 
canal  was  Daemon ;  the  lake,  Lacus  Phoenicis.  The 
canals  were  first  recorded  in  large  numbers  by  Schia- 
parelli  in  1877 ;  the  lakes,  at  the  Harvard  station  in 
Arequipa  in  1892,  when  forty  of  them  were  observed. 

A  large  telescope  is  not  necessary  in  order  to  see 
clearly  the  canals  and  lakes.  One  of  eight  or  ten 
inches  aperture  is  ample.  The  really  important 
requisite,  however,  is  a  steady  atmosphere,  such  as 
is  found  only  in  low  latitudes,  which  gives  what  as- 
tronomers technically  call  "good  seeing."  This  ex- 
plains why  it  is  that  Mars  cannot  be  studied  to  ad- 
vantage at  the  large  northern  observatories,  where, 
with  the  most  superb  optical  equipment,  little  or 
nothing  save  the  coarser  detail  can  be  seen  upon  its 
surface. 

Doubt  has  recently  been  expressed,  in  some  of  the 


132  Mars 

foreign  periodicals,  even  as  to  the  existence  of  the 
canals.  An  astronomer  who  has  never  looked  through 
a  telescope,  except  in  northern  Europe  or  the  eastern 
United  States,  has  no  right  to  express  any  opinion 
on  the  subject,  because  he  simply  does  not  know  what 
good  seeing  looks  like,  and  his  opinion  is  therefore 
valueless.  He  might  as  well  express  his  views  on 
electro-dynamics  or  physiology.  The  comparatively 
small  number  of  astronomers  who  are  familiar  with 
good  seeing,  and  have  looked  at  Mars,  have  seen  the 
canals,  and  consequently  do  not  doubt  their  exist- 
ence. 

Our  present  telescopes  are  plenty  large  enough 
for  purposes  of  planetary  research;  indeed,  some  of 
them  are  too  large,  and  no  gain  can  be  secured  by 
trying  to  improve  them.  In  Cambridge  an  aperture 
of  6  inches  will  show  everything  on  the  Moon  or 
Mars  that  can  be  seen  with  a  15-inch  telescope.  At 
Flagstaff,  where  the  seeing  is  much  better,  Professor 
Lowell  has  stated  that  he  often  reduces  his  aperture 
from  24  to  16  inches  in  order  to  see  more  distinctly. 
What  we  must  now  do  is  to  try  to  find  places  on  the 
Earth  where  the  seeing  is  better  than  anything  yet 
discovered,  and  erect  our  future  telescopes  there. 
Then  we  can  perhaps  use  still  larger  apertures  to 
advantage.  Heat  or  moisture  have  nothing  what- 
ever to  do  with  the  seeing;  it  is  chiefly  a  question  of 
latitude;  and  in  low  latitudes,  such  as  Arequipa 


What  We  Know  About  Mars  133 

—  16°,  and  Flagstaff  +  36°,  the  seeing  is  often 
very  good  indeed.  The  reason  of  this  is  that  these 
places  are  far  removed  from  the  great  cyclonic  dis- 
turbances which  affect  our  atmosphere  in  the  tem- 
perate zones.  At  these  places,  the  canals  of  Mars 
are  perfectly  distinct.  To  understand  how  the 
planet  appears  there  through  a  large  telescope,  we 
may  examine  the  Moon  some  night  through  a  small 
opera  glass.  The  sharpness  and  amount  of  detail 
visible  in  the  two  cases  will  be  similar,  although  the 
appearance  of  the  two  bodies  is  quite  unlike. 

In  former  times  the  red  color  of  the  planet  was 
supposed  to  be  due  to  its  atmosphere.  Later  it  was 
seen  that  this  was  impossible.  The  dark  spots  on 
its  surface  were  next  thought  to  be  water,  and  were 
called  seas ;  while  the  bright  red  areas  were  supposed 
to  be  due  to  vegetation,  which  it  was  imagined  must 
be  of  that  color  upon  Mars.  Later  the  writer  sug- 
gested that  the  so-called  seas  and  canals  were  the 
real  vegetation,  the  red  areas  being  desert  regions.7 
This  view  was  strongly  confirmed  by  the  Arequipa 
observations  of  1892,  and  the  Flagstaff  observations 
of  1894,  and  has  since  been  generally  adopted,  al- 
though the  old  names,  for  the  sake  of  their  con- 
venience, are  still  retained. 

One  out  of  several  difficulties  in  supposing  that  the 

T  Science,  1888,  12,  83.  Astronomy  and  Astro-Physics,  1892, 
11,  670. 


134  Mars 

seas  and  canals  are  due  to  water,  is  that  many  of 
the  canals  cross  the  seas,  which  it  is  difficult  to  ex- 
plain on  that  hypothesis  (see  Figs  5  and  11).  Some 
of  the  lakes  on  the  planet,  also,  are  located  in  the 
seas.  The  latter  are  found  to  be  a  vivid  green  in 
what  corresponds  to  the  springtime  of  Mars.  After- 
wards they  turn  grey;  and  still  later  those  of  them 
near  the  poles  become  yellow.  They  are  then  distin- 
guished only  with  difficulty  from  the  soil  of  the  desert 
regions  of  the  planet.  In  a  recent  observation  made 
at  this  season  by  Lowell  at  Flagstaff,  the  Mare 
Erythrseum  was  found  to  have  turned  a  chocolate 
brown,  a  color  which  on  the  Earth  we  should  asso- 
ciate with  fertility.  The  writer  has  seen  the  same 
color  exhibited  at  the  time  of  the  drying  up  of  the 
temporary  south  polar  ocean.  The  canals  are  usu- 
ally too  narrow  to  have  any  appreciable  color,  al- 
though in  the  case  of  the  broader  ones  their  color 
is  thought  sometimes  to  resemble  that  of  the  seas. 
Sometimes  it  is  described  by  both  Schiaparelli  and 
Lowell  as  brown. 

Their  breadth  is  very  uncertain;  some  observers 
like  Douglass  draw  them  very  wide  (see  Fig.  5)  ; 
others  like  Lowell,  from  whose  drawing  Fig.  6  is 
copied,  extremely  narrow.  The  writer  gives  them  an 
intermediate  breadth  (see  Fig.  10).  Occasionally, 
with  conditions  favorable  to  the  best  seeing,  short 
and  extremely  narrow  canals  have  been  seen  by  the 


FIG.     5.       REGION    ABOUT    SYRTIS 

MAJOR 
Drawn  by  A.  E.  Douglass 


What  We  Know  About  Mars  135 

writer  (Fig.  3)  ;  but  the  long  canals  never  appear 
to  him  as  narrow  as  they  are  drawn  by  Lowell. 


FIG.  6.     REGION  ABOUT  SYRTIS      FIG.     7.     MARKINGS    ON     THE 

MAJOR  SURFACE  OF  MARS 

From  a  drawing  by  Professor          Drawn  by  writer  from  two 
Lowell.  photographs    taken    at    Flag- 

staff. 

Recently  Mr.  Lampland  at  Flagstaff  has  suc- 
ceeded in  photographing  some  of  the  canals.  At  first 
it  was  supposed  that  these  photographs  would  serve 
to  convince  the  doubters  of  their  existence ;  but  it 
was  soon  found  that  those  who  doubted  the  canals 
were  also  unable  to  see  them  on  the  photographs,  so 
that  the  photographic  argument  seemed  to  have  a 
minus  value.  Photographically  the  canals  are  ex- 
tremely difficult  objects,  and  it  does  not  surprise  the 
writer  that  those  unused  to  astronomical  photo- 
graphs, could  not  make  them  out. 

A  drawing  from  the  photographs  was  made  by  Mr. 
Wesley  and  published  in  The  Observatory  the  past 
year.  Fig.  7  is  a  drawing  by  the  writer,  based 


136  Mars 

chiefly  on  the  third,  but  partly  on  the  first  photo- 
graph issued  in  Bulletin  No.  21  of  the  Lowell  Ob- 
servatory. The  other  photographs  were  also  con- 
sulted, and  no  marking  was  considered  assured  which 
did  not  appear  upon  at  least  one  of  the  others. 
These  photographs  were  taken  about  an  hour  after 
the  drawing  by  Professor  Lowell  (Fig.  6)  was  made. 
A  comparison  of  the  two  shows  very  clearly  a  tend- 
ency on  his  part  to  draw  the  detail  too  small,  in 
comparison  with  the  diameter  of  the  disc. 


FIG.  8.     KEY  MAP  GIVING  NAMES  OF  CANALS  AND  OTHER 
FEATURES 

Fig.  8  will  serve  as  a  key  to  the  names  of  the 
canals  discussed,  which  Lowell  states  are  visible  on 
the  photograph.  The  main  features — Hellas,  Mare 
Erythrseum,  Mare  Icarium,  and  Syrtis  Major — are 
all  obvious  on  the  originals  from  which  Fig.  7  was 
sketched.  The  canals  Nilosyrtis,  Casius,  and  Pyra- 
mus  are  also  perfectly  clear,  but,  it  will  be  noticed, 
do  not  appear  on  the  photograph  as  canals  at  all, 


What  We  Know  About  Mars  137 

but  as  broad  areas.  Regarding  the  last  two,  this 
is  true  also  of  Lowell's  drawing.  His  drawing  of 
the  first  is  certainly  too  narrow,  as  proved  by  the 
photographs.  Of  the  remaining  canals  described  by 
him — which  come  down  as  narrow  lines  in  the  photo- 
graph— Thoth,  Astaborus,  and  Protonilus  are  fairly 
clear.  Vexillum,  Pierius,  and  Ismenius  Lacus  are 
more  difficult,  but  apparently  shown. 

As  a  photographic  triumph,  these  results  are  well 
worthy  of  record ;  and  when  we  consider  how  difficult 
it  is  to  photograph  fine  detail  that  is  not  merely 
obvious  but  even  conspicuous  to  the  eye,  the  photo- 
graphs bear  strong  testimony  to  the  distinctness  with 
which  the  canals  must  have  been  visible  at  Flagstaff 
on  the  day  in  question. 

Intermediate  between  the  doubters  and  Professor 
Lowell's  immediate  following,  there  is  a  large  class 
of  persons  who  deny  some  of  the  fainter  canals,  and 
who  doubt  the  uniformity  of  structure  of  the  others. 
They  say  his  canals  are  too  regular,  too  narrow,  and 
too  straight — that  if  they  were  better  seen  they 
would  be  found  to  be  made  up  of  short  broken  lines 
of  varying  width,  and  perhaps,  in  places,  of  irregu- 
lar spots.  This  proves  to  be  the  case  with  the  lunar 
canals.  With  poor  seeing  and  a  low  magnification, 
they  seem  to  be  perfectly  smooth  and  straight,  like 
the  Martian  ones ;  but  with  good  seeing  and  a  higher 
power,  they  are  found  to  be  quite  irregular.  Why 


138  Mars 

should  it  not  be  true  also  on  Mars?  To  this,  Mr. 
Lowell  replies  that  the  lunar  canals  consist  of  dark 
markings  lying  along  natural  cracks,  while  the  Mar- 
tian canals  are  artificial.  This  may  be  so,  but  it 
would  be  hard  to  prove  it. 

Again,  amidst  numerous  irregular  and  nearly  in- 
visible markings,  the  human  eye,  when  straining  for 
the  faintest  possible  detail,  naturally  connects  con- 
spicuous objects  by  straight  lines.  Is  it  not  possible 
therefore  that  many  of  these  fainter  canals  are 
merely  subjective  effects? 

The  point  of  all  this  criticism  is  that  the  numer- 
ous long,  straight  lines  give  the  planet  a  very  arti- 
ficial appearance.  If  the  lines  were  more  broken  and 
irregular,  they  would  look  more  like  natural  mark- 
ings, more  in  fact  like  what  we  find  upon  the  Moon. 
In  short,  the  argument  in  favor  of  intelligent  inhabi- 
tants would  be  greatly  weakened. 

DUPLICATION    OF    THE    CANALS 

In  1882,  Schiaparelli  announced  that  the  canals 
in  Mars  were  sometimes  double.  One  day  a  canal 
would  be  clearly  seen,  on  the  next  day,  or  even  a  few 
hours  later,  there  would  be  two  in  its  place.  Later 
the  two  would  disappear,  and  again  the  canal  would 
be  single.  Sometimes  the  single  canal  would  coin- 
cide with  one  of  the  pair,  but  more  frequently  it 


What  We  Know  About  Mars  1S9 

would  coincide  with  neither  of  them.  When  we  con- 
sider that  these  double  canals  were  often  as  much  as 
200  miles  apart,  these  sudden  changes  seemed  in- 
credible. 


FIG.  9.    DUPLICATE  CANALS,  FROM  DRAWING  BY  PROFESSOR 

LOWELL 

Opposition  of  1903.  Sinus  Sabsecus  is  near  top  of  disc;  Syrtis 
Major  on  the  left. 

When  Lowell  confirmed  the  duplication  of  the  ca- 
nals (see  Fig.  9),  many  astronomers  hesitated  to  ac- 
cept it.  In  fact  his  observations  even  seemed  to  make 
it  still  more  improbable.  He  measured  their  separa- 
tion with  telescopes  of  different  apertures,  and  suc- 
ceeded in  seeing  the  duplication  when  both  by  theory 
and  observation  it  should  have  been  invisible.  More- 
over, with  a  few  exceptions,  the  only  drawings  he 
published  showing  the  double  canals  were  made  by 
himself;  and  these  exceptions  were  mostly  made  by 
Douglass,  who,  in  the  published  text,  expressed  grave 
doubts  as  to  the  objective  reality  of  the  duplica- 


140  Mars 

tion.  It  is  true,  several  other  observers  using  much 
smaller  telescopes  claimed  to  see  it;  but  it  always 
happened  to  be  just  at  the  limit  of  visibility  of  their 
telescopes,  no  matter  what  the  size  of  their  instru- 
ments chanced  to  be.  One  of  the  most  skilful  of  these 
observers,  M.  Antoniadi,  later  published  his  doubts 
as  to  the  genuineness  of  what  he  had  seen.  On  the 
other  hand,  most  of  the  observers  who  used  large 
telescopes  always  saw  the  canals  single.  Naturally 
the  astronomers  were  not  convinced. 

Now  further  observations  have  been  made,  and 
new  facts  brought  to  light  that  partially  explain  this 
singular  phenomenon.  According  to  Professor 
Lowell  only  about  one-quarter  of  all  the  canals  are 
ever  seen  to  be  double,  and  they  are  probably  double 
all  the  time.8  It  is  only  when  they  are  very  faint 
that  they  appear  single,  and  their  faintness  is  ap- 
parently the  reason  that  the  duplication  does  not 
then  show.  This  is  due  to  the  fact  that  under  these 
circumstances  one  canal  is  somewhat  fainter  than 
the  other,  and  so  escapes  detection.  According  to 
his  views,  the  single  canal  always  coincides  in  posi- 
tion with  one  of  the  two  components  of  the  double. 

The  double  canals  usually  appear,  he  says,  as  a 
broad,  hazy  band;  it  is  only  by  glimpses  that  the 
duplication  is  seen.  There  is  nothing  improbable 
in  the  idea  that  one-quarter  of  the  canals  should  be 

"Lowell  Observatory  Bulletin  No.  15. 


What  We  Know  About  Man  141 

permanently  broad  and  the  rest  permanently  nar- 
row. The  only  question  is,  Is  it  likely  that  either 
the  middle  of  these  canals  should  fade  out,  leaving 
the  sides  dark,  or  that  the  sides  should  darken,  leav- 
ing the  middle  bright? 

It  is  a  fact  that  some  of  the  seas,  as  the  season 
progresses,  will  fade  out  across  the  middle  in  places, 
leaving  the  rest  dark,  and  thus  present  on  a  com- 
paratively large  scale  a  phenomenon  similar  to  that 
claimed  for  the  double  canals.  This  same  effect  oc- 
curs upon  the  floor  of  the  lunar  crater  Eratosthenes, 
forming  two  widely  diverging  canals.  A  long,  double 
canal  is  also  found  upon  the  rim  of  this  crater,  but 
this  is  clearly  due  to  the  presence  of  two  long,  paral- 
lel cracks.  A  similar  chance  occurrence  might  oc- 
casionally be  found  upon  Mars,  but  it  seems  to  the 
writer  in  the  light  of  the  facts,  and  especially  of  the 
opinions  of  Messrs.  Douglass  and  Antoniadi,  that 
the  case  for  a  systematic  duplication  will  not  be 
proved  until  more  well-known  observers,  favorably 
situated  and  circumstanced,  have  recorded  it. 


SEASONAL  CHANGES 

Perhaps  Lowell's  most  interesting  recent  investi- 
gation is  on  what  he  calls  the  Cartouches  of  the 
Canals — that  is,  their  variable  visibility  dependent 


Mart 

on  the  Martian  seasons.9  He  finds  that  soon  after 
the  begnining  of  the  melting  of  the  northern  ice-cap, 
the  canals  begin  to  develop  in  the  north  polar  re- 
gions. These  are  immediately  followed  by  the  ca- 
nals in  the  north  temperate  zone.  A  few  weeks  later, 
those  in  the  torrid  zone  develop;  and  still  later, 
those  in  the  south  temperate.  The  process  of  de- 
velopment, therefore,  is  carried  on  across  the  equa- 
tor. This  is  most  naturally  explained  by  the  growth 
of  vegetation  following  the  annual  transference  of 
water  from  pole  to  pole.  The  speed  of  transfer  he 
finds  is  at  the  rate  of  two  miles  per  hour. 

The  striking  difference  between  Mars  and  our 
planet  is  that  in  our  equatorial  regions,  where  we 
have  plenty  of  water,  there  is  continued  fertility 
throughout  the  year.  On  Mars  the  vegetation  must 
wait  until  the  water  reaches  it  semi-annually  from 
the  poles.  There  are  accordingly  two  fertile  and 
two  barren  seasons. 

Professor  Lowell  concludes  that  the  water  is  trans- 
ferred artificially  from  pole  to  pole.  In  this  we  can 
hardly  follow  him,  since  with  the  rare  atmosphere, 
and  accordingly  rapid  evaporation  and  condensa- 
tion upon  Mars,  the  aqueous  vapor  would  necessarily 
flow  across  the  planet's  surface  of  itself,  being  al- 
ternately condensed  at  each  pole  by  the  winter's 
cold. 

•Lowell  Observatory  Bulletin  No.  12. 


What  We  Know  About  Mart  143 

A  curious  feature  of  the  canals  and  other  mark- 
ings is  that  they  do  not  always  present  the  same  ap- 
pearance at  the  same  equivalent  time  in  successive 
Martian  years.  Thus,  a  certain  marking  called  by 
Schiaparelli  "Lacus  Maris"  could  not  be  found  at 
all  at  Arequipa  in  1892.  After  an  interval  of  thir- 
teen years  since  it  had  last  been  seen,  it  reappeared 
with  perfect  distinctness  in  1903,  and  was  observed 
by  Lowell.10  A  very  marked  change  in  the  Deuca- 
lionis  Regio,  observed  in  1892  in  connection  with 
the  melting  of  the  ice-cap,  did  not  take  place  again 
at  the  same  equivalent  season  in  1894;  nor  has  it 
been  observed  since.  A  certain  canal  observed  by 
Schiaparelli  was  not  found  at  all  by  Lowell,  an- 
other one  having  replaced  it.  This  latter  only  re- 
cently disappeared,  Schiaparelli's  original  canal  hav- 
ing taken  its  place. 

IS    THE    PLANET    INHABITED    BY   INTELLIGENT    BEINGS? 

There  is  little  doubt  now  that  Mars  possesses  vege- 
table, and  perhaps  animal  life,  but  the  question  that 
interests  humanity  is,  Are  there  intelligent  beings 
there?  The  only  important  argument  in  favor  of 
their  existence  is  the  presence  of  the  canals.  These 
canals  are  so  long  and  narrow,  straight  and  uni- 
form, that  they  look  artificial.  If  they  are  artificial, 

10  Lowell  Observatory  Bulletin  No.  8. 


144  Man 

it  is  certain  that  their  constructors  possess  a  knowl- 
edge of  spherical  trigonometry,  and  considerable  skill 
in  the  mechanical  construction  of  surveying  instru- 
ments, implying  greater  intelligence  than  that  pos- 
sessed by  our  ancestors  a  thousand  years  ago.  It  is 
doubtful  if  our  progenitors  in  the  year  900  A.  D. 
could  have  built  a  perfectly  straight  road  three 
thousand  miles  long,  directed  to  a  definite  point, 
even  ^f  it  had  been  across  level  country. 

But  is  the  evidence  sufficient  as  yet  to  warrant  us 
in  pronouncing  in  favor  of  such  intelligent  beings? 
Doubtless  the  temptation  to  do  so  is  very  strong,  but 
that  should  not  influence  our  judgment.  It  is  a  gen- 
eral principle  of  science  that  when  two  explanations 
of  a  phenomenon  are  possible,  we  should,  other  things 
being  equal,  choose  the  simpler.  Lowell's  maps  of 
Mars  look  very  artificial  but  we  must  remem- 
ber that  they  are  composites  of  many  drawings,  such 
as  are  given  in  this  article.  All  the  canals  shown 
on  the  maps  are  not  seen  at  once;  on  the  contrary, 
only  a  very  few  of  them  are  visible  on  the  same  night. 
It  seems  to  the  writer  that  the  arguments  both  for 
and  against  intelligent  inhabitants  have  been  mate- 
rially strengthened  during  the  past  few  years.  It 
does  not  seem  to  him,  however,  that  on  either  side 
are  they  conclusive.  The  reader  must  therefore 
choose  for  himself  between  them. 

Let  us  suppose  that  there  are  intelligent  inhabi- 


What  We  Know  About  Mars  145 

tants.  One  can  imagine,  in  the  seasonal  transfer  of 
the  water  across  the  equator,  that  a  portion  of  the 
moisture,  condensed  from  the  air  each  night  as  a 
heavy  dew,  is  deposited  on  the  ground  and  perhaps 
on  sparsely  growing  and  therefore  invisible  vegeta- 
tion, in  the  desert  regions.  From  that  rare  atmos- 
phere, consisting  largely  of  aqueous  vapor,  so  much 
may  be  condensed  in  the  more  elevated  areas  as  to 
flow  in  invisible  channels  to  the  larger  canals,  caus- 
ing the  vegetation  there  to  develop,  and  thus  become 
visible.  A  good  deal  of  the  moisture  would  sink 
into  the  soil,  but  this  would  the  next  day  be  eva- 
porated by  the  Sun's  heat,  and  continue  on  its  course 
to  the  winter  pole.  This  explanation,  of  course,  does 
not  necessarily  involve  the  existence  of  intelligent  in- 
habitants ;  but  without  them  the  canals  would  almost 
certainly  in  the  course  of  time  lose  their  straight- 
ness  and  artificial  aspect. 

The  other  explanation  of  the  canals  is  that  they 
are  due  to  the  same  causes  that  produce  those  on 
the  Moon.  As  seen  through  the  telescope  they  look 
exactly  like  them,  save  that  the  Martian  canals  are 
much  longer  and  somewhat  wider.  The  lunar  canals 
seldom  exceed  ten  miles  in  length.  They  radiate  from 
small  lakes  and  join  large  seas  precisely  like  the 
Martian  areas,  and  are  equally  straight  and  artificial 
looking  in  appearance.  They  wax  and  wane  with  the 
seasons  in  the  same  way.  The  Moon  is  so  near  that 


146  Mart 

we  can  study  them  to  advantage.  The  foundations 
of  the  lakes  are  minute  craterlets ;  of  the  canals,  fine 
cracks.  As  the  season  progresses,  dark  areas  form 
about  them  and  later  fade  out.  The  explanation 
offered  is  that  moisture  is  given  out  by  the  cracks, 
which  is  later  absorbed.  This  moisture  nourishes 
the  vegetation  to  which  the  darkening  is  due.  Ex- 
actly similar  cracks,  causing  similar  vegetational  ca- 
nals, are  found  in  Hawaii.  One  characteristic  canal 
was  estimated  by  the  writer  at  two  or  three  yards  in 
width,  by  thirty  in  length.  The  terrestrial  and  lu- 
nar canals  are  certainly  produced  without  intelli- 
gent assistance. 

In  conclusion,  we  may  say  that  while  we  have  not 
as  yet  sufficient  information  to  settle  this  ques- 
tion definitely,  information  is  slowly  accumulating, 
largely  owing  to  Professor  Lowell's  indefatigable  in- 
dustry, which  will  doubtless  decide  it  in  time.  His 
observatory  is  the  only  one  at  present  specially  de- 
voted to  securing  an  answer  to  it,  and  it  seems  al- 
most a  pity  that  some  other  favorably  located  obser- 
vatory should  not  devote  some  of  its  time  to  the 
same  object. 


CHAPTER  XIV 

DIFFERENT    EXPLANATIONS    OF   THE 
CANALS  OF  MARS  1 

Leaving  aside  the  older  and  now  generally  dis- 
credited explanations  that  the  canals  are  gigantic 
water  channels,  that  they  are  cracks  in  a  universal 
covering  of  ice,  and  that  they  are  grooves  cut  by 
colliding  asteroids,  we  will  turn  to  the  explanations 
held  as  more  probable  by  the  astronomers  of  the 
present  day. 

Much  of  the  oldest  of  these  2  considers  them  to 
be  caused  by  narrow  ditches,  which,  crossing  the 
desert  regions  of  the  planet,  furnish  water  to  vege- 
tation growing  along  their  banks.  It  is  these  com- 
paratively broad  bands  of  vegetation,  and  not  the 
narrow  water-channels  themselves,  which  are  visible 
in  our  telescopes.  The  chief  advocate  of  this  view 
at  the  present  time  is  Professor  Lowell,  who  has 
adopted  it  as  the  foundation  of  his  theories  of 
Martian  civilization.  A  serious  objection  to  the 

1  Harper's  Monthly,  1908,  192. 
'Science,  1888,  12,  82. 

147 


148  Mart 

hypothesis  is  the  difficulty  of  forcing  water  through 
the  canals  for  thousands  of  miles,  over  a  compara- 
tively level  country.  Professor  Lowell  gets  over  this 
difficulty  by  stating  that  it  is  pumped  through  them 
artificially.  Many  astronomers  recoil  from  an  arti- 
ficial explanation,  where  it  is  possible  to  account 
for  the  phenomena  observed  by  any  natural  method. 
The  difficulty  of  transporting  the  water  is  fur- 
ther enhanced  if  we  consider  the  fact,  which  is  gen- 
erally admitted,  that  the  amount  of  atmosphere  we 
find  on  Mars  does  not  exceed  one-quarter  the  quan- 
tity per  square  mile  of  surface  that  we  find  upon 
the  Earth.  This  view  is  based  largely  on  Professor 
Campbell's  spectroscopic  investigations,  confirmed 
by  the  clearness  with  which  we  see  the  details  of  the 
planet's  surface.  Since  gravity  upon  Mars  is  but 
three-eighths  of  what  it  is  upon  the  Earth,  the 
atmospheric  pressure  on  the  Martian  surface  can- 
not exceed  three  thirty-seconds  of  our  own,  or  71 
millimeters  of  mercury.  Under  this  low  pressure 
water  boils  at  113°  Fahr.  If  the  amount  of  atmo- 
sphere on  Mars  is  only  one-tenth  as  much  as  that 
on  the  Earth,  which  is  highly  probable,  the  boiling 
point  of  water  upon  the  surface  of  the  planet  would 
be  reduced  to  84°  Fahr.  That  the  daylight  tem- 
perature of  the  surface  does  not  differ  greatly  from 
our  own,  we  know  by  the  rapidity  with  which  the 
polar  ice-caps  disappear  on  the  approach  of  sum- 


{Different  Explanations  of  the  Canals     149 

mer.  It  would,  therefore,  seem  that  the  evaporation 
of  water  from  the  surface  must  proceed  with  extra- 
ordinary rapidity,  and  the  difficulty  of  transporting 
it  through  canals,  and  supplying  sufficient  for  the 
needs  of  vegetation  upon  the  way,  must  be  accord- 
ingly greatly  enhanced. 

Indeed,  it  would  seem  necessary  to  substitute 
gigantic  water-mains  for  the  canals,  with  a  most 
extended  system  of  supplementary  piping.  The 
amount  of  power  required  to  pump  sufficient  water 
to  irrigate  anywhere  between  100,000  and  1,000,000 
square  miles  of  surface,  through  such  a  system  of 
piping,  may  be  left  to  any  competent  hydraulic 
engineer  to  compute,  with  the  added  statement  that 
most  of  the  water  is  to  be  transported  to  a  distance 
exceeding  1,000  miles. 

If  we  are  to  insist  on  a  Martian  civilization  at 
all  hazards,  a  more  defensible  explanation  of  the 
canals  might  be  founded  on  the  photograph  shown 
in  Fig.  1.  This  photograph  was  obtained  by  the 
writer  during  the  past  summer  while  on  a  vacation 
trip  in  the  Azores.  It  represents  a  somewhat  insig- 
nificant hill  known  as  Cabe£o  Gordo,  which  was 
passed  on  the  way  to  the  summit  of  the  volcano 
Pico,  near  Fayal. 

There  is  a  bush  or  low  tree,  known  as  the  urze, 
which  grows  on  the  slopes  of  the  volcano,  and 
which  is  analogous  in  character  to  our  pines  and 


150  Mars 

spruces.  This  hill  was  originally  covered  with  it, 
but  most  of  it  has  now  been  cut  down  by  the  shep- 
herds in  order  to  afford  pasturage  to  their  flocks. 
Narrow  areas  of  it  have  been  permitted  to  stand, 
however,  in  order  to  furnish  protection  to  the  ani- 
mals against  the  terrific  winter  winds  sometimes 
occurring  at  these  altitudes. 

Similar  markings  might  very  readily  be  produced 
artificially  on  Mars,  and  we  are  not  even  obliged  to 
assume  that  any  portion  of  its  surface  is  of  a  desert 
character.  It  must  be  remembered  that  the  canals 
of  Mars  are  not  a  few  feet  but  several  miles  in 
breadth.  Imagine  that  the  whole  surface  of  the 
planet  was  originally  covered  with  some  form  of 
bush  or  tree,  which  in  the  northern  and  equatorial 
regions  has  now  been  largely  destroyed.  Its  con- 
tinued presence  in  the  southern  regions  would  ac- 
count for  the  so-called  seas,  while  narrow,  more  or 
less  continuous,  strips  of  it  would  account  for  the 
canals. 

The  vegetation,  both  field  and  woodland,  would 
be  supported  by  the  atmospheric  circulation,  just 
as  it  is  upon  the  Earth,  and  no  gigantic  engineering 
feats  whatever  are  required  of  the  assumed  inhab- 
itants. Why  the  inhabitants  of  Mars  should  grow 
their  vegetation  in  these  peculiar  forms,  the  writer 
does  not  pretend  to  know,  but  very  likely  the  same 
reason  that  influences  the  shepherds  of 


FIG.    1.      CABECO   GORDO,   A   HILL  IN  THE   AZORES,   SHOWING   CANAI^ 
LIKE   MARKINGS 


FIG.    5.       A    CANAL-LIKE    MARKING    PRODUCED    NATURALLY    IN    THE 
DESERTS    OF   HAWAII    BY    AN    ACTIVE    STEAM-CRACK 


\Different  Explanations  of  the  Canals     151 

Gordo,    protection    against    severe    winter    climate, 
may  be  the  explanation. 

But  is  it  necessary  to  assume  a  Martian  civiliza- 
tion? Astronomers  generally  think  not.  The  only 
argument  in  its  favor  is  the  artificial  appearance 
of  the  drawings  of  the  canal  system  of  the  planet. 
What  the  public  generally  does  not  understand, 
however,  is  that  while  the  drawings  may  look  thor- 
oughly artificial,  and  may  be  most  carefully  made, 
yet  that  the  planet  itself,  if  sufficiently  well  seen, 
might  not  look  artificial  at  all.  The  statement 
sometimes  made  that  the  canals  really  consist  of 
straight  uniform  lines  is  by  no  means  generally 
accepted  by  astronomers.  In  fact,  as  we  shall  pres- 
ently see,  what  evidence  we  have  points  quite  in 
the  opposite  direction. 

•  immune 

FIG.  2.     A  SERIES  OF  DOTS  WHICH  AT  A  DISTAKCE  OF  30  FEKT 
LOOKS  LIKE  A  CONTINUOUS  LINE 

If  we  make  a  horizontal  row  of  dots  or  vertical 
lines  on  a  piece  of  paper  (Fig.  2),  the  distance  be- 
tween their  centres  being  one-eighth  of  an  inch,  and 
if  we  view  them  from  a  distance  of  thirty  feet,  they 
will  appear  to  our  eyes  simply  as  a  continuous, 
uniform,  horizontal  line.  If  we  scatter  a  sufficient 
number  of  dots  and  lines  irregularly  over  the  paper 


152 


Mars 


(Fig.  3),  and  view  them  also  from  a  distance  of 
thirty  feet,  it  will  be  possible  for  us,  after  a  careful 
examination,  to  see  the  three  chief  dots  connected 
as  shown  by  the  heavy  lines,  (Fig.  4).  At  a  suitable 
distance  these  lines  will  appear  perfectly  straight 
and  uniform.  If  we  approach  somewhat  nearer,  the 
finer  lines  will  appear.  These  lines  have  a  very 
artificial  aspect,  and  yet,  if  we  view  the  original 
(Fig.  3)  close  at  hand,  we  shall  see  that  the  drawing 
really  represents  nothing  but  an  irregular  grouping 
of  spots. 

Photographs  of  fine  planetary  or  lunar  detail 
are  much  more  unreliable  than  drawings,  because 
they  have  to  be  on  so  small  a  scale  in  proportion 
to  what  is  known  to  photographers  as  the  "grain" 


FIGS.  3  AND  4.  IRREGULAR  MARKINGS  SUCH  AS  ARE  SHOWN  IN 
FIG  3,  WHEN  SEEN  FROM  A  DISTANCE  OF  30  FEET,  RE- 
SEMBLE THE  CANALS  OF  FIG.  4 


Different  Explanations  of  the  Canals     153 

of  the  plate.  This  grain  is  a  sort  of  irregular  back- 
ground, which  becomes  very  conspicuous  as  soon  as 
the  plate  is  sufficiently  enlarged.  Atmospheric  diffi- 
culties and  irregular  motions  of  the  driving-clock 
of  the  telescope  are  also  much  more  serious  to  the 
photographer  than  to  the  visual  astronomer.  For 
these  reasons  astronomers  generally  consider,  that 
it  was  a  great  triumph  for  the  photographers  of  the 
Lowell  Observatory  to  be  able  to  get  any  indica- 
tions of  the  canals  whatever  upon  their  plates.  As 
far  as  a  detailed  study  of  the  planet's  surface  is 
concerned,  however,  the  Lowell  drawings  are  of  much 
more  value  than  the  Lowell  photographs. 

As  to  the  so-called  doubling  of  the  canals,  most 
astronomers  simply  decline  to  admit  the  existence 
of  the  phenomenon,  on  the  visual  and  photographic 
evidence  so  far  presented.  That  out  of  several  hun- 
dred canals  one  or  two  might  be  double  from  merely 
accidental  causes  is  not  denied,  but  the  demonstra- 
tion of  the  duplication  of  any  large  proportion, 
such  as  one-fourth,  as  claimed  by  Professor  Lowell, 
is  awaited  with  interest. 

But  if  we  deny  that  the  canals  are  artificial,  how 
then  can  they  be  explained?  The  alternative  hypo- 
thesis,3 and  the  one  which  it  is  believed  from  the 
writer's  private  correspondence  is  generally  pre- 
ferred by  those  astronomers  interested  in  Mars,  is 

*  Popular  Astronomy,  1904, 12,  439. 


154  Mars 

that  the  canals  are  due  to  volcanic  cracks  lying 
between  craterlets  on  the  Martian  surface.  Water 
vapor  escaping  from  these  craterlets  and  cracks 
nourishes  the  vegetation  growing  along  their  sides, 
and  it  is  this  vegetation  which  is  visible  in  our  tele- 
scopes. 

This  latter  view  has  the  distinct  advantage  that 
it  also  explains  the  canals  on  the  Moon,  which,  as 
seen  through  a  small  telescope,  are  indistinguishable 
from  those  on  Mars.  They  also  go  through  the 
same  changes  and  transformations  in  the  course  of 
a  lunation  that  the  Martian  canals  do  in  the  course 
of  the  Martian  year,  and  differ  from  them  only  in 
the  fact  that  they  are  on  a  much  smaller  scale. 
Through  a  large  telescope,  with  good  atmospheric 
conditions,  the  craterlets  and  cracks  about  which 
the  lunar  lakes  and  canals  are  formed  can  be  dis- 
tinctly seen,  and  the  gradual  transformation  of  a 
crack  into  a  canal  has  been  watched,  and  the  rate 
of  growth  of  the  latter  measured.4  Through  a 
small  telescope  the  lunar  canals,  like  the  Martian 
ones,  appear  straight  and  perfectly  uniform. 
Through  a  large  glass,  on  the  other  hand,  irregu- 
larities of  outline  appear,  and  marked  variations 
in  the  depth  of  color. 

Similar  natural  canals  formed  about  terrestrial 

4  Annals  Harvard  College  Observatory,  53,  78.  Memoirs 
American  Academy,  1906,  13,  176. 


FIG.  6.    THE  ARIAD^US  RILL,  A  STRAIGHT  VOL- 
CANIC CRACK  UPON  THE  MOON,   150  MILES  IN 
LENGTH 

(Photographed   at   Yerkes   Observatory   with   40-inch 
telescope) 


iDifferent  Explanations  of  the  Canals     155 

volcanic  cracks  have  been  studied  and  photographed 
in  Hawaii.  See  Fig.  5.5  This  view  represents  a  por- 
tion of  the  desert  extending  to  the  south  of  Kilauea. 
The  only  vegetation  growing  upon  it  consists  of 
trees,  low  bushes,  and  ferns,  which  stretch  across 
it  in  long,  narrow,  straight  lines,  following  the  course 
of  the  steam  cracks,  whose  exhalations  furnish  the 
necessary  moisture  on  which  the  existence  of  the 
vegetation  depends. 

Stretching  across  Fig.  6  is  shown  the  Ariadaeus 
rill,  a  volcanic  crack  upon  the  Moon  150  miles  in 
length.  If  it  were  still  giving  out  steam,  we  should 
doubtless  have  here  a  straight  lunar  canal  quite 
comparable  in  size  to  many  of  those  found  on  Mars. 
About  one  thousand  of  these  rills,  most  of  them 
much  smaller  than  this  one,  are  now  catalogued 
upon  the  Moon. 

The  objection  that  most  astronomers  feel  to  the 
admission  of  the  existence  of  civilization  upon  Mars 
is  not,  it  seems  to  the  writer,  a  sort  of  jealousy  of 
the  other  planets,  such  as  Professor  Lowell  has  sug- 
gested and  a  wish  that  intelligence  should  be  con- 
fined to  our  Earth.  On  the  contrary,  trustworthy 
evidence  of  its  existence  would  certainly  be  welcomed 
by  them,  as  by  everyone  else,  not  only  with  pleasure, 
but  with  wild  enthusiasm.  Their  feeling,  I  believe, 
is  rather  that  the  four  planets,  Venus,  the  Earth, 

•  See  Figure  5,  facing  p.  150. 


156  Mart 

the  Moon,  and  Mars,  are  all  of  about  the  same  size 
and  are  situated  at  similar  distances  from  the  Sun. 
Their  surface  conditions  must  therefore  bear  a  gen- 
eral resemblance  to  one  another.  Life  is  so  per- 
sistent, and  will  exist  under  such  varied  conditions, 
that  it  is  not  surprising  that  it  should  be  found  on 
all  of  them.  Indeed,  as  we  have  seen,  we  have  already 
pretty  strong  visual  evidence  that  it  does  exist  on 
two  of  them  besides  the  Earth.  As  compared  with 
vegetation,  it  seems  probable  that  human  life,  or  its 
planetary  equivalent,  would  have  much  more  nar- 
row limits.  Vegetable  life  beneath  the  sea,  for  in- 
stance, is,  as  we  all  know,  very  luxuriant.  The  pos- 
sible limits  of  civilization  are  still  more  narrow  than 
those  of  human  life. 

Under  the  reduced  atmospheric  pressure  and 
probable  almost  total  lack  of  free  oxygen  upon 
Mars,  we  can  still  see  no  reason  why  vegetation 
should  fail  to  exist.  But  is  it  likely  that  civilization 
should  be  found  there  also?  We  do  not  definitely 
deny  that  some  form  of  civilization  under  these  cir- 
cumstances might  be  possible,  but  why  invoke  its 
aid  to  explain  the  various  observed  phenomena,  such 
as  the  canals,  if  we  can  furnish  a  better,  or  even 
nearly  as  good,  explanation  of  them  by  some  other 
hypothesis  ? 

The  physical  conditions  on  Mars  are  in  many 
ways  intermediate  between  those  found  upon  the 


Different  Explanation*  of  the  Canal*     157 

Earth  and  the  Moon,  and  it  seems  plausible  that 
the  life  existing  upon  it  should  similarly  be  of  a 
higher  type  than  that  found  on  the  Moon,  and  of 
a  lower  type  than  that  found  at  present  on  the  sur- 
face of  the  Earth.  Even  if  the  physical  conditions, 
as  we  understand  them,  were  equally  favorable  with 
those  on  the  Earth,  civilization  would  by  no  means 
be  a  necessary  consequence.  Had  it  not  been  settled 
by  Europeans,  the  United  States  would  still  be  a 
wilderness.  How  much  less  should  we  hasten  to 
accord  civilization  to  a  planet  of  which  we  know 
little,  except  that  if  we  were  transported  there  our- 
selves, we  should  instantly  die. 


CHAPTER   XV 
SIGNALLING  TO  MARS  l 

Although  this  computation  was  first  made  by  the 
writer  for  his  own  amusement,  nearly  twenty  years 
ago,  it  had  never  seemed  to  him  of  sufficient  interest 
or  importance  to  the  astronomical  world  to  publish 
it  anywhere,  and  he  would  not  do  so  now,  had  not 
his  definite  statements  on  the  subject  been  directly 
called  in  question.  By  the  term  "possibility  of  com- 
munication with  a  remote  planet"  the  writer  means 
that  if  a  portion  of  the  human  race,  with  their  pres- 
ent knowledge  and  appliances  were  removed  to  that 
planet,  and  could  live  there,  that  it  would  be  pos- 
sible to  communicate  with  them.  Whether  there  are 
intelligent  beings  on  Mars  or  on  any  other  planet, 
the  writer  does  not  know.  That  is  an  entirely  sep- 
arate question,  and  has  nothing  whatever  to  do  with 
the  case. 

The  constants  required  in  our  computation  are  as 
follows : — 

1  Popular  Astronomy,  1909,  17,  495. 
158 


Signalling  to  Mars  159 

*S=Mean  distance  from  the  Earth 

to  the  Sun 92,900,000  miles 

Af=Mean  distance  of  Mars  to  the 

Sun 141,500,000  miles 

D=Mean    diameter    of    the    Sun 

from  the  Earth 1,922" 

Z,=Stellar      magnitude      of      the 

Sun   -26.83  miles 

The  computation  is  made  when  Mars  is  situated 
in  quadrature  with  the  Sun.  In  this  position  its 
mean  distance  from  the  Earth,  M,  is  108,000,000 
miles.  Let  us  imagine  a  mirror  erected  upon  the 
Earth  of  such  a  size  that  the  whole  disk  of  the  Sun 
can  be  seen  in  it  from  Mars.  Let  d  be  the  diameter 
of  the  Sun  as  seen  in  the  mirror,  and  I  its  magni- 
tude. Then, 

DS 

d  = =  888" 

S  +  M 
and 

1  =  2.5   (log   (S+M)2— log &)+L——  25.15 

Let  us  now  imagine  this  mirror  so  reduced  in  size 
as  to  reflect  a  circular  beam  whose  diameter  is  only 
1 00%  MO  of  that  of  the  Sun's  disk.  As  seen 
from  Mars  the  diameter  of  this  beam  will  be 


160  Mart 

0".00089,  and  its  brightness,  which  will  be  reduced 
30  magnitudes,  4.85.  The  diameter  on  the  Earth  of 
such  a  beam  will  be  a  trifle  less  than  half  a  mile. 
Therefore,  allowing  for  absorption  and  an  inclined 
mirror,  the  sunlight  reflected  from  an  area  of  mir- 
rors a  little  over  half  a  mile  square  would  appear  to 
Mars,  when  in  quadrature,  of  the  brightness  of  a 
star  of  the  fifth  magnitude.  When  Mars  was  forty- 
five  degrees  from  opposition,  and  its  distance  from 
the  Earth  was  61,000,000  miles,  such  a  beam  would 
be  brighter  than  the  fourth  magnitude. 

This  light  would,  of  course,  be  very  conspicuous 
from  Mars  with  the  naked  eye,  were  it  not  for  the 
brightness  of  the  Earth  itself.  This  materially  modi- 
fies the  problem.  By  holding  a  mirror  so  as  to  cover 
half  of  the  area  of  a  6-inch  objective,  and  by  so 
doing  projecting  the  image  of  a  star  of  the  2.8  mag- 
nitude upon  the  disk  of  the  Moon,  the  star  was 
found  to  be  just  visible  with  a  2.5-inch  eye-piece. 
With  a  higher  power  and  steadier  mirror,  much  bet- 
ter results  would  have  been  obtained,  but  on  this 
basis  a  24-inch  objective  should  be  able  to  show  a 
star  of  the  6.5  magnitude  when  projected  upon  the 
disks  of  the  Earth  or  Moon.  The  object  of  using 
a  higher  power  would  be  to  reduce  the  light  of  the 
Moon  without  diminishing  that  of  the  star.  With 
four  times  the  power,  a  signal  of  the  8.0  magnitude 


Signalling  to  Mars  161 

should  readily  be  detected,  even  after  allowing  for 
some  magnification  of  the  star  image  itself. 

It  therefore  appears  not  only  that  the  plan  of  sig- 
nalling to  Mars  by  the  system  proposed  is  "scien- 
tifically plausible,"  but  that  if  it  were  adopted,  we 
should  produce  a  signal  that  would  be  three  to  four 
magnitudes,  that  is  16  to  40  times  brighter  than 
necessary,  and  would,  therefore,  be  dazzlingly  con- 
spicuous to  Martian  observers,  if  they  were  intel- 
lectually and  physically  our  equals. 

In  closing,  the  writer  would  only  add  that  this 
plan  of  signalling  to  Mars  is  not  now,  and  never  has 
been  (as  is  shown  by  a  large  portion  of  the  con- 
temporary press),  advocated  by  the  writer,  until 
after  we  shall  have  obtained  more  definite  informa- 
tion that  there  are  intelligent  inhabitants  upon  Mars. 


CHAPTER  XVI 
THE  CANALS  OF  MARS * 

In  the  issue  of  the  Scientific  American  of  July 
10th,  a  correspondent  argues  that  the  discovery  of 
the  gradual  shifting  of  position  of  some  of  the  canals 
of  Mars  helps  to  strengthen,  instead  of  weakening, 
the  theory  of  irrigating  ditches.  It  does  undoubtedly 
strengthen  all  the  theories  of  the  canals  based  on 
the  idea  that  they  are  strips  of  vegetation,  and  it 
also  incidentally  strengthens  the  idea  that  their  for- 
mation and  maintenance  may  be  due  to  the  efforts 
of  intelligent  life  upon  the  planet.  But  it  weakens 
the  explanation  of  irrigating  ditches,  as  compared 
with  some  of  the  other  theories. 

Let  us  now  consider  some  of  these,  which  assume 
the  existence  upon  Mars  of  intelligence  analogous 
to  our  own.  Let  us  first  discuss  one  of  those  based 
on  the  idea  that  the  lack  of  water  is  really  the  chief 
necessity  felt  upon  the  planet.  According  to  this 
theory,  invisible  water  vapor  is  evaporated  by  the 
heat  of  the  sun  from  the  snowy  pole  in  the  spring- 

'  Scientific  American,  1915, 113,  246. 
162 


The  Canals  of  Mars  163 

time  and  transported  by  the  planetary  circulation 
to  the  other  pole,  where  the  sun  is  setting  for  the 
long  winter  night.  Here  the  vapor,  which  forms  a 
much  larger  proportion  of  the  planet's  atmosphere 
than  with  us,  is  condensed  as  snow,  a  constant  dis- 
tillation going  on  by  the  sun's  heat  from  one  pole 
to  the  other,  and  then  back  again,  every  year. 
Dtiring  the  nighttime  a  portion  of  this  traveling 
vapor  is  deposited  as  fog  over  the  level  regions.  In 
many  cases  these  elongated  areas  may  lie  in  slightly 
depressed  regions  or  valleys,  where  the  fog  would 
naturally  accumulate  of  itself.  In  the  early  morn- 
ing on  Mars,  where  the  sun  is  rising,  we  can  Dome- 
times  see  the  fog  clear  away,  and  it  is  in  these 
moistened  regions  that  the  vegetation  springs  up  and 
forms  the  so-called  canals. 

But  while  the  lack  of  water  appears  at  first  sight 
to  be  the  chief  necessity  of  Mars,  judged  by  terres- 
trial standards,  yet  such  may  not  really  be  the  case 
at  all,  and  we  might  suggest  that  other  needs  may 
be  much  more  pressing.  Besides  water,  vegetation 
requires  several  solid  constituents,  the  chief  of  which, 
applied  as  fertilizers,  are  alkalies,  phosphates,  and 
nitrates.  On  account  of  its  small  atomic  weight, 
nitrogen  in  the  gaseous  form  must  certainly  be 
rather  rare  on  Mars.  We  are  just  beginning  on  the 
earth  to  have  to  use  our  atmospheric  nitrogen  as 
a  source  of  nitrates  for  fertilizers.  It  may  easily  be 


164?  Mars 

that  the  Martians  have  not  sufficient  quantities  of  it 
or  of  some  other  of  these  solid  constituents  to  en- 
able them  to  fertilize  the  whole  surface  of  their 
planet,  and  they  therefore  distribute  their  fertilizer 
as  widely  as  they  can  in  those  places  where  it  will 
do  the  most  good,  occasionally  shifting  their  crops 
to  fresh  regions  of  the  planet. 

Still  another  theory,  also  involving  artificial  direc- 
tion, may  be  based  on  the  fact  that,  besides  solids 
and  water,  vegetation  requires  two  gases  for  its 
existence — oxygen  and  carbon-dioxide.  While  a  very 
important  part  of  the  work  of  plant  life  is  the  break- 
ing up  of  the  latter  gas  and  the  evolution  of  free 
oxygen,  yet  oxygen  is  itself  consumed  in  considerable 
quantities  by  vegetation,  just  as  it  is  by  animals. 
We  know  that  there  is  not  very  much  atmosphere 
on  Mars,  and  oxygen  must  be  scarce. 

But,  besides  the  oxygen,  it  is  quite  possible  that 
the  carbon-dioxide,  too,  may  be  lacking.  On  our 
own  earth  this  necessary  food  for  vegetation  is  pro- 
vided, not  as  is  sometimes  supposed,  chiefly  by  the 
breathing  of  the  animal  world,  but  by  our  more  or 
less  active  volcanoes.  Animal  life,  indeed,  furnishes 
only  an  insignificant  fraction  of  the  total  supply. 
Mars  is  an  ancient  world,  and  any  volcanoes  that  it 
formerly  possessed  may  now  very  likely  be  entirely 
extinct.  In  such  a  case  all  the  carbon-dioxide  re- 
quired by  vegetation  must  be  supplied  by  the  animal 


The  Canals  of  Mars  165 

world,  by  combustion,  or  possibly  by  some  other 
chemical  process.  To  maintain  the  proper  balance 
between  animal  and  vegetable  life,  it  is  clear  that 
the  latter  must  be  more  or  less  limited.  All  useless 
vegetation  would  be  destroyed,  and  such  as  was  left 
would  only  be  permitted  to  grow  in  the  most  favor- 
able and  necessary  places.  Indeed,  we  find  that  the 
canals  which  when  they  first  appear  are  very  wide, 
gradually  narrow  as  the  season  progresses,  and  this 
very  narrowing  may  itself  be  a  visible  indication  to 
us  of  the  activities  of  the  Martians ! 

It  is  generally  believed  that  the  southern  hemi- 
sphere of  Mars  is  situated  at  a  slightly  lower  level 
than  the  northern  one.  This  is  indicated  by  observa- 
tions of  the  Martian  terminator.  This  difference 
of  level  has  been  given  as  the  explanation  for  the 
observed  fact  that  most  of  the  Martian  vegetation 
is  confined  to  the  southern  hemisphere.  This  expla- 
nation would  be  particularly  applicable  if  there  were 
a  shortage  of  carbon-dioxide  on  the  planet,  as  it  is 
well  known  that  this  gas  always  tends  to  collect,  on 
account  of  its  high  specific  gravity,  in  any  deep 
depressions  of  the  earth's  surface. 

Each  one  of  these  theories  accounts  for  the  canals 
found  upon  the  planet  and  for  their  distribution 
chiefly  in  the  northern  hemisphere,  as  well  as  for 
their  shifting  and  narrowing  with  the  progress  of 
the  seasons.  If  we  once  admit  the  existence  of  intel- 


166  Mars 

ligent  life  on  Mars,  since  we  have  no  means  what- 
ever of  knowing  what  are  their  chief  needs,  it  be- 
comes useless  for  us  to  theorize  further  upon  their 
reasons  for  constructing  the  canals,  otherwise  than 
to  say  that  they  indicate  a  shortage  of  supplies  for 
vegetation. 

Whichever  need  may  be  most  felt,  whether  water, 
nitrogen  or  carbon-dioxide,  it  appears  that  the  can- 
als are  calculated  to  meet  it,  and  are  what  we  might 
ourselves  construct  or  plant  under  similar  circum- 
stances. 

All  of  these  theories  avoid  the  necessity  of  enor- 
mous conduits  and  the  expenditure  of  an  amount  of 
work  in  pumping,  which  has  recently  been  estimated 
by  an  expert  adherent  of  the  pumping  hypothesis 
at  2,500,000,000  horse-power,  or  four  thousand 
times  that  of  Niagara  Falls. 

The  reason  that  the  writer  stated  in  a  former 
paper,  that  the  irrigation  conduit  theory  was  not 
strengthened  by  the  shifting  the  canals,  was  that 
the  number  of  conduits  would  have  to  be  increased 
if  the  canals  shifted.  This  does  not,  of  course,  dis- 
prove the  conduit  theory,  but  certainly  does  not 
strengthen  it,  as  compared  with  the  other  theories 
explaining  the  canals,  where  no  such  added  construc- 
tion is  necessary. 


CHAPTER  XVII 
MARS— THINGS  KNOWN  AND   SURMISED1 

It  is  a  rather  difficult  matter  to  distinguish  what 
is  known  from  what  is  surmised  about  any  subject, 
but  if  we  define  what  is  known  about  Mars  as  mean- 
ing what  is  generally  believed  about  it  by  profes- 
sional astronomers,  and  what  is  surmised  as  what  at 
the  present  time  seems  most  probable,  the  writer 
thinks  that  present  Martian  views  may  be  summar- 
ized rather  briefly. 

We  have,  first,  the  astronomical  data,  which  are 
certainly  known,  and  are  approximately  as  follows: 
The  distance  of  the  planet  from  the  sun  is  one  and 
a  half  times  as  great  as  that  of  the  earth.  Its  year 
is  687  of  our  days,  or  nearly  two  of  our  years.  Its 
orbit  is  very  eccentric,  so  that  it  is  sometimes  much 
nearer  to  the  sun  than  at  others.  Its  diameter  is  a 
little  over  forty-two  hundred  miles.  Its  mass  is  one- 
ninth,  and  its  surface  gravity  about  two-fifths,  that 
of  the  earth.  This  latter  quantity  is  most  impor- 
tant in  determining  its  supply  of  water  and  atmos- 

1  Cosmopolitan,  Oct.,  1909,  616. 
167 


168  Mars 

phere,  and  therefore  its  habitability.  The  inclina- 
tion of  its  equator  to  its  orbit  is  practically  the  same 
as  that  of  the  earth.  Hence  its  seasons  are  similar, 
except  that  they  are  nearly  twice  as  long  as  our  own. 
Its  period  of  rotation  upon  its  axis,  that  is  to  say, 
its  day,  expressed  in  terrestrial  units,  is  twenty-four 
hours  and  thirty-seven  minutes. 

Most  astronomers  would  probably  accept  the  fol- 
lowing statements  as  true :  The  planet  possesses  white 
polar  caps,  which  increase  in  winter  and  diminish 
in  summer.  These  are  due  to  ice.  When  they  are 
melting  most  rapidly  they  are  surrounded  by  a  dark 
ring  of  water,  which  soon  disappears.  This  is  the 
only  water  visible  upon  the  planet.  The  melting  ice 
fixes  the  temperature  at  this  time,  which  is  32° 
Fahrenheit.  The  atmosphere  is  extremely  rare. 
This  involves  great  extremes  of  temperature,  a  rapid 
evaporation  of  the  water  in  the  daytime,  and  a  very 
rapid  deposition  of  dew  or  frost  at  night.  The 
climate  from  our  standpoint  must,  therefore,  be  ex- 
tremely disagreeable,  even  at  the  equator.  While 
never  very  hot,  it  must  at  night  be  extremely  cold. 
The  atmosphere  is  much  more  rare  than  upon  our 
highest  mountain  summits,  and  would,  therefore,  be 
quite  unbreathable  by  terrestrial  animals.  Clouds 
have  been  observed  floating  over  the  surface  of  the 
planet,  and  their  speed  and  direction  measured.  Ex- 
cept at  sunrise  and  sunset  they  are  of  rare  occur- 


Mars — Things  Known  and  Surmised       169 

rence,  although  they  are  observed  more  frequently 
at  the  time  of  the  melting  of  the  polar  caps. 

The  dark  surface  markings  of  the  planet  consist 
of  the  so-called  seas,  canals,  and  lakes,  which  last 
are  also  known  as  oases.  The  light  surface  mark- 
ings consist  of  the  so-called  deserts,  causeways,  and 
white  spots.  Those  astronomers  who  attempt  to  ex- 
plain them  at  all  consider  them  to  represent  differ- 
ent densities  of  vegetation.  The  writer  believes  the 
white  spots  to  be  due  to  a  form  of  vegetation  equiva- 
lent to  our  flowering  plants.  These  spots  appear  for 
a  few  weeks  in  the  summer  time  near  the  tropics. 

The  above  summarizes  practically  all  that  we 
know,  and  all  that  we  may  properly  surmise,  with 
regard  to  Mars.  To  those  who  are  in  any  way  in- 
terested in  the  planet,  the  matter  of  most  vital  im- 
portance, at  present,  is  the  question,  Are  any  of  these 
surface  markings  artificial?  Certainly  they  may  be. 
We  have  no  definite  proof  to  the  contrary,  but  any 
statement  at  the  present  time  ascribing  them  di- 
rectly to  intelligent  beings  must  be  clearly  under- 
stood to  be  no  better  than  a  speculation. 

What  then  can  we  do  to  settle  this  question?  To 
many  persons  this  is  a  matter  of  serious  importance. 
All  who  have  seen  the  canals  clearly,  must  admit  that 
they  have  an  artificial  aspect.  That  is  to  say,  they 
are  not  sinuous  in  shape,  but  are  fairly  straight. 
Moreover,  they  are  of  pretty  uniform  breadth  and 


170  Mars 

density.  This  would  all  appear  very  favorable  to 
an  artificial  origin,  but  unfortunately  it  so  hap- 
pens that  there  are  canals  upon  the  moon  which 
appear  equally  straight  and  equally  artificial,  al- 
though much  smaller.  They  also  appear  and  dis- 
appear with  the  seasons.  The  lunar  canals  certainly 
cannot  be  artificial.  Similar  canals  on  a  still  smaller 
scale  have  been  found  in  the  'Hawaiian  Islands.  They 
are  due  to  vegetation  along  volcanic  cracks  crossing 
a  desert  region.  The  steam  emitted  from  these 
cracks  supports  the  vegetation,  which  would  other- 
wise wither  and  die.  The  question  at  once  arises 
whether  it  is  possible  that  the  lunar  and  Martian 
canals  are  due  to  this  same  cause. 

Few  astronomers  now  deny  the  existence  of  the 
Martian  canals.  The  question  for  us  to  settle  is  not, 
Do  they  exist?  but,  How  do  they  look?  To  settle 
this  does  not  require  a  gigantic  telescope,  but  it  does 
require  an  especially  good  atmosphere.  Such  an 
atmosphere  can  only  be  found  in  a  low  latitude.  A 
five-inch  telescope  in  Jamaica  shows  much  finer 
planetary  detatil  than  a  fifteen-inch  telescope  in 
Cambridge.  A  large  telescope  erected  in  our  north- 
ern states  would  be  absolutely  useless  for  the  pur- 
pose in  hand.  Indeed,  it  would  probably  be  unde- 
sirable in  any  location.  Perhaps  the  best  results 
would  be  obtained  with  a  moderate-sized  telescope  of 
about  twenty-four  inches  aperture,  which  is  the  size 


Mars — Things  Known  and  Surmised      171 

of  the  instrument  which  has  been  erected  by  Prof. 
Percival  Lowell  in  the  clear  atmosphere  of  Flagstaff, 
Arizona.  Given  such  an  instrument  in  an  ideal  lo- 
cality, how  should  it  be  used? 

A  man  who  has  good  eyesight,  or  who  is  a  skilful 
astronomer,  is  not  necessarily  a  good  artist.  This 
point  has  been  quite  overlooked  by  the  public  hith- 
erto. Yet  it  is  of  the  utmost  importance  if  we  wish 
to  know  exactly  how  the  canals  appear.  To  settle 
this  question  a  number  of  experienced  astronomers 
should  be  invited  to  sketch  the  canals  as  seen  by 
them  through  this  same  telescope,  located  under 
these  extremely  favorable  conditions.  Astronomers 
with  some  little  experience  in  sketching  planetary  or 
lunar  details  should  be  selected  by  preference.  Be- 
sides the  astronomers,  a  number  of  artists  skilled  in 
miniature  work  should  also  be  invited  to  study  the 
planet.  Probably  none  of  these  men  would  secure 
results  of  much  value  during  the  first  week  of  their 
observations,  because  it  requires  a  special  training 
acquired  only  by  practice  to  enable  one  really  to  un- 
derstand what  he  does  see  in  this  class  of  work.  Dur- 
ing the  second  week  of  this  work,  however,  more  valu- 
able results  would  be  secured. 

Studies  of  both  the  lunar  and  Martian  canals 
should  be  made  by  each  observer,  and  finally  the  best 
results  of  each  man  should  be  selected  and  published. 
When  this  has  been  done,  then  not  only  astronomers, 


172  Mars 

but  the  public  at  large,  will  have  a  fair  opportunity 
to  judge  for  themselves  of  the  appearance  of  the  de- 
tail of  the  planet,  and  decide  whether  or  not  it  is 
probable  that  the  canals  of  Mars  are  the  work  of 
intelligent  beings.  This  is  certainly  the  next  step 
that  should  be  taken  in  our  investigation  of  this  most 
interesting  planet. 


INDEX 


Associated  observers,  19. 
Atmosphere,    12,    20,  59,    126, 
148. 

Blue  color  of  water,  40,  48,  48, 

57,  99,  100. 

Canals,  Description  of,  83,  86. 
Duplication,  58,  6T,  89,  113, 

138,  153. 
Explanation  of,  14,  42,  43, 

58,  76,   87,    95,    103,    108, 
111,  133,  138,  145,  147,149, 
162,  170. 

Lunar,  105,  109. 

Shifting,  18. 

Width  of,   19,  84,  89,   104, 

134. 
Changes  visible,  18,  39,  42,  48, 

58,  84,  97,  99,  142. 
Climate,  13,  78. 
Clouds,  13,  17,  55,  57,  58,  60, 

128,  130. 
Color  changes,  38,  45,  57,  81, 

100,  118. 

Colors  visible,  18,  26,  45,  57, 
79. 

Data  regarding  planet,  11, 120, 

167. 
Depressions  on  terminator, 

101. 
Deserts,  14,  45. 


Ellipticity  of  disc,  59. 

Facts    regarding    planet,    11, 
57,  120,  167. 

History  of  discoveries,  64,  131. 
Horse  power  for  irrigation,  15, 

Lakes,  19,  58,  62,  83,  86. 

Lunar,  109,  137,  145. 
Life,  Intelligent,  92,  143,  155, 
164. 

Marshes,  12,  17,  81. 
Meteorology,  78. 

Photographs   of    planet,    129, 

135. 
Polarization,  43,  99. 

Seas,  14,  44,  72,  79,  124. 
Signalling  to  Mars,  158. 
Snow,  12,  21,  32,  46,  60,  68, 
116,  124. 

Telescopic  apertures,  131,  170. 
Temperature,  24,  75,  127. 

Vegetation,  14,  43,  45, 101, 108, 
130,  133,  134,  142. 

Water      transferred      across 
planet,  15,  74. 


173 


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